Book - The Pineal Organ (1940) Glossary

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Gladstone RJ. and Wakeley C. The Pineal Organ. (1940) Bailliere, Tindall & Cox, London. PDF

   The Pineal Organ (1940): 1 Introduction | 2 Historical Sketch | 3 Types of Vertebrate and Invertebrate Eyes | Eyes of Invertebrates: 4 Coelenterates | 5 Flat worms | 6 Round worms | 7 Rotifers | 8 Molluscoida | 9 Echinoderms | 10 Annulata | 11 Arthropods | 12 Molluscs | 13 Eyes of Types which are intermediate between Vertebrates and Invertebrates | 14 Hemichorda | 15 Urochorda | 16 Cephalochorda | The Pineal System of Vertebrates: 17 Cyclostomes | 18 Fishes | 19 Amphibians | 20 Reptiles | 21 Birds | 22 Mammals | 23 Geological Evidence of Median Eyes in Vertebrates and Invertebrates | 24 Relation of the Median to the Lateral Eyes | The Human Pineal Organ : 25 Development and Histogenesis | 26 Structure of the Adult Organ | 27 Position and Anatomical Relations of the Adult Pineal Organ | 28 Function of the Pineal Body | 29 Pathology of Pineal Tumours | 30 Symptomatology and Diagnosis of Pineal Tumours | 31 Treatment, including the Surgical Approach to the Pineal Organ, and its Removal: Operative Technique | 32 Clinical Cases | 33 General Conclusions | Glossary | Bibliography
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The Pineal Organ


Acanthias (Gr. acantha, spine) : a genus of sharks including the spiny dogfish, so named from the spines on the dorsal fins.

Acanthopterygii (Gr. acantha, spine ; pterux, wing or fin) : fishes with spinous rays supporting the paired fins, e.g. perch.

Acarina (Gr. akari, mite) : a division of the Arachnida, of which the cheesemite is a type.

Acilius caliginosus : a beetle belonging to the family Dyticidas, Order Coleoptera.

Acipenser (L. — a large fish commonly taken to be sturgeon) : genus of Ganoids including the sturgeon.

Acone eyes (Gr. a, without ; konos, cone) : retina; of invertebrate animals in which there are no crystalline cones, as in many insects, e.g. Coleoptera, Diptera.

Actinozoa (Gr. actin, ray ; zodn, animal) : a division of the Coelenterata, of which the sea-anemones are a type, and which show a radial symmetry.

Adiadochokinesia (Gr. a, absence of; diadoche, succession; kinesis, movement) : inability to perform successive movements, such as rapid and repeated pronation and supination of the two forearms.

Agelena labyrinthica : a cellar spider belonging to the Order Araneida.

Agnathi (Gr. a, without ; gnathos, jaw) : the branch of craniate vertebrates which includes the Ostracodermi or Cyclostomata and characterized by the absence of jaws.

Amblystoma (Gr. amblus, blunt ; stoma, mouth) : a tailed amphibian, the permanent larval form of which is the Mexican Axolotl, having a blunt nose.

Ami a (Gr. amia, a kind of tunny) : a bony fish allied to the mackerels.

Ammoccetes (Gr. ammos, sand ; ketos, fish) : the larval form of Petromyzon, lamprey.

Ammonites (Gr. ammon, (ram's) horn, symbol of Zeus-Ammon) : the fossil shells of the extinct Cephalopoda, usually referred to the subclass Tetrabranchiata. Their spiral shells resemble that of the living genus Nautilus.

Amphioxus (Gr. amphi, both ; oxus, sharp) : the lancelet fish, so named on account of its being pointed at both ends. It belongs to the subclass Cephalochorda.

Amphipoda (Gr. amphi, both ; pons, foot) : an order of the Crustacea, comprising the sand-hoppers and fresh- water shrimps. The feet are directed both forwards and backwards.

Anapsida (Gr. a, an, without ; apsis, arch) : the name applied to a primitive type of reptile in which the roof of the skull is complete, without a temporal fossa, as in the Stegocephala. See : Synapsida ; Diapsida.



Anaspida (Gr. a, an, without ; aspis, shield) : an order of extinct fishes belonging to the branch Ostracodermi, characterized by the absence of a headshield.

Anguis fragilis (L. anguis, snake ; fragilis, brittle) : blindworm, a snake-like, limbless lizard with imperfectly developed eyes.

Annelida (Gallicised form of Annulata) : ringed worms, without jointed feet, and comprising the sub-classes Chaetopoda and Hirudinea.

Annulosa (L. annuhts, ring) : sub-kingdom comprising the Anarthropoda and Arthropoda in which the body consists of a succession of rings.

Anomodontia (Gr. anomos, without order or irregular ; odous, tooth) : an extinct order of reptiles, also called Dicynodontia, with large teeth resembling a dog's canines.

Anoura (Gr. a, an, without ; oura, tail) : tailless amphibia, e.g. frogs and toads.

Apus Cancriformis (Gr. a, without ; pons, foot ; L. cancer, crab ; forma, shape) : a small fresh-water crustacean characterized by a dorsal shield and crab-like form.

Arachnida (Gr. arachne, web ; arachnes, spider) : air-breathing Arthropoda, including the spiders and scorpions.

Argonauta (Gr. argos, living without labour ; naute, sailor) : the female " paper nautilus," a dibranchiate cephalopod, with a corrugated spiral shell in which the animal floats idly on the surface of the water.

Argulus : the carp louse, an external parasitic Copepod, crustacean, having a trilobate median eye and compound lateral eyes.

Arthrodira (Gr. arthron, joint ; deire, neck) : an order of extinct fishes including Coccosteus, Dinichthys, and Titanichthys ; they are characterized by a joint separating the head-shield from the body-shield.

Arthropoda (Gr. arthron, joint ; pons, foot) : an invertebrate phylum characterized by jointed limbs, as contrasted with " bristle " feet.

Ascidia (Gr. askos, bottle ; eidos, like) : an order of the class Tunicata, with sac-like bodies, comprising the sea-squirts.

Ascidia mammillata (Gr. askos, bottle ; eidos, shape) : a Tunicate the freeswimming larva of which contains a single eye enclosed within the ventricular cavity of the brain.

Astacus fluviatilis : fresh-water crayfish, belonging to the order Decapoda of the class Crustacea.

Astroscopus (Gr. astron, stars ; skopeo, look) : the American star-gazer. An electric ray in which the eyes are situated close together and directed upwards. The electric organs are on the dorsal surface of the head just behind the eyes. Auchenaspis (Gr. auchen, narrow, neck ; aspis, shield) : an extinct palaeozoic fish belonging to the class Ostracodermi. It had paired lateral orbital cavities, between which are two small pineal canals. Aurelia aurita (L. aureolns, golden colour ; anrita, long-eared) : the common jelly-fish, so named on account of its colour and the ear-shaped form of its oral arms. Axolotl : the persistent larva of Amblystoma, which retains its external branchiae throughout life. 3i


Balanoglossus (Gr. balanos, acorn ; glossa, tongue) : a worm-like animal, having a tongue-like proboscis and rudimentary notochord, belonging to the class Hemichorda, of the Protochordata. The larval form, or Tornaria, closely resembles the trochophore larvae of certain invertebrates.

Bdellostoma (Gr. bdella, leech ; stoma, mouth) : a genus of the Myxinoidei, including the hag-fishes, so named on account of the leech-like mouth.

Belone (Gr. " sharp " — fish with pointed nose) : the gar-pike and bony-pike, Lepidosteus.

BiBiONiDAi : a group of insects in which the males possess two pairs of compound eyes — an upper, larger with coarse facets, and lower, smaller with fine facets. The two larger eyes are contiguous or united. Carriere considers that the small lower eye of the male corresponds to the whole eye of the female.

Blastocyst (Gr. blastos, bud or germ ; kuste, bladder, sac) : the stage of development in which the embryo consists of a single layered vesicle.

Blastopore (Gr. blastos, germ) : the opening leading into the cavity of a gastrula.

Bombinator (Gr. bombos, L. bombus, a humming or croaking sound) : a genus of European toads.

Brachiopoda (Gr. brachion, arm ; pous, foot) : a class of the Molluscoida having two fleshy arms, continued from the sides of the mouth. It includes the lamp-shells and barnacles.

Branchiopoda (Gr. branchia, gill ; pons, foot) : a division of the Crustacea comprising the orders Cladocera, Phyllopoda, and Trilobita, and characterized by gills supported by the feet.

Branchiosaurus (Gr. branchia, gill ; saura, lizard) : a genus of extinct Stegocephala.

Branchipus (Gr. branchia, gill ; pous, foot) : a crustacean belonging to the order Phyllopoda ; the group includes the brine-shrimps ; the transparent body is unprotected by a carapace.

Oecilia (L. Caecilia), the slow-worm or blind worm, from caecus, blind. A group of limbless amphibians, with vestigial eyes, e.g. Ichthyophis glutinosus.

Cainozoic (Gr. kainos, recent ; zoos, living, life) : the Kainozoic or Tertiary period of geology, applied to recent formations in which the organic remains resemble more or less closely existing animals and plants.

Cambrian System or Period (Welsh ; Cambria, Cymry) : the earliest Palaeozoic rocks, which lie below the Silurian in Wales and Cumberland. It contains marine invertebrates, including the earliest forms of trilobites.

Capitosaurus (L. caput, head ; Gr. saura, lizard) : a genus of extinct stegocephalous amphibia.

Carapace (Gr. cara, head ; karabos, beetle ; L. scarabceus ; carabus locusta) : a protective covering for the head or dorsal aspect of the body.

Carboniferous (L. carbo, coal ; fero, bear) : the Palaeozoic period, lying above the Old Red Sandstone (Devonian) and below the Permian. It is characterized by the presence of coal and the appearance of amphibia.


Cephalaspis (Gr. kephale, head ; aspis, shield) : an extinct genus of fishes

belonging to the order Osteostraci of the class Ostracodermi. Cephalic apodeme (Gr. kephale, head ; apo, with ; demas, body or frame)

the internal skeleton of the head, present in some arthropods and

molluscs. Cephalopoda (Gr. kephale, head ; pous, foot) : a class of Mollusca which

includes the cuttle-fishes, squids, octopuses, and nautili. Ceratodus (Gr. keras, horn ; odous, tooth) : a genus of the lung fishes or

Dipnoi (Australia). Ch/ETOGNATha (Gr. chaite, bristle ; gnathos, jaw) : an order of the phylum

Nematohelminthes, or Round-worms, comprising the marine arrow

worms (Sagitta). Chelae, Chelate (Gr. chile, claw) : the prehensile claws which are present

on some of the limbs of certain Crustacea, e.g. the lobsters and

crabs. Chelonia (Gr. chelone, a tortoise) : an order of the class Reptilia, comprising

the tortoise and turtles. Chelydra (Gr. chelus, like a tortoise ; udor, water) : a genus of turtles or

water tortoises. Chimara (Gr. chimaira, monster) : a primitive type of deep-water fish belonging to the order Holocephali. Chitin (Gr. chiton, cuirass) : a nitrogenous horny material, which is deposited

in the outer epithelial layers of certain invertebrate animals, to form a

hard, protective covering, as in the exoskeleton of the Crustacea. Chiton (Gr. chiton, coat of mail) : a genus belonging to the class Amphineura

of the Mollusca. The back is covered by a jointed shield. Chondrichthyes (Gr. chondros, cartilage ; ichthus, fish) : cartilaginous fishes,

including the sharks and rays. Chondrostei (Gr. chondros, cartilage ; osteon, bone) : an order of Ganoid

fishes comprising the sturgeons and spoon-bill, characterized by few

replacing bones. Chromatophore (Gr. chroma, colour ; phoreo, carry) : connective tissue cells

found in the derma and other mesodermal tissues, which contain large

pigment granules and are often branched. Cirripedia (L. cirrus, a tuft or crest of curled hair or feathers ; pes, foot) : an

order of the Ostracoda including the barnacles, in which eyes are afivays

wanting in the adult fixed-form of the animal. Both median and lateral

eyes, however, may be present in the Cypris larva, e.g. Lepas fascicular is. Cistella (L. cistella, small box) : a Brachiopod in which the upper valve of the

shell articulates with the lower by a horizontal hinge. It contains a

shelly-loop for the support of the lophophore. The trochophore larva

has one or two pairs of ocelli. Cladocera (Gr. klados, branch ; keras, horn) : an order of Crustacea having

branched antenna;, including Daphnia and Polyphemus. Coccosteus (Gr. kokkos, berry, kernel ; osteon, bone) : a genus of extinct

fishes belonging to the order Arthrodira.


Ccelenterata (Gr. koilos, hollow ; enter on, bowel) : the phylum which comprises the polyps, sea-anemones, and jelly-fishes, in which there is an enteric cavity lined by entoderm.

Coleoptera (Gr. koleos, sheath ; pteron, wing) : an order of the Insecta — beetles in which the anterior pair of wings are modified to form a hard, protective covering for the posterior membranous wings.

Compound eye : a term which is applied in two senses — (1) An eye consisting of several strata of cells, e.g. (a) receptive (rod and cone cells), (b) intermediate (bipolar cells), (c) retinal ganglionic cells ; (2) a composite or aggregate eye in which the whole is composed of an aggregate of units, each of which is called an ommatidium.

Conarium (Gr. konarion, dim. of konos, cone) : the epiphysis cerebri, so named on account of the conical form in man and certain mammals.

Convergence : the acquisition of a similar form or structure by two or more different organisms as a result of a similar mode of life ; as contrasted with resemblances which are due to inheritance from a common ancestor.

Copiophora cornuta (Gr. kopis, a curved knife, sting ; phoreo, bear ; L. cornuta, horned) : a species of locust in which there is a single, median frontal ocellus of large size.

Coregonus : a genus of fresh-water fishes belonging to the family Salmonidae ; commonly known as " white fish."

Corneagen cells (L. cornu, horn ; rt. gen, give origin to) : the epidermal cells which produce the superficial non-cellular or horny layer. When the cells form a single stratum of tall columnar cells, this layer is sometimes spoken of as the palisade layer.

Crangon : sea-water shrimp belonging to the sub-class Malacostraca, or softshelled crustaceans.

Cretaceous System or Period (L. creta, chalk) : the uppermost chalky deposits of the mesozoic or secondary era, in which remains of bony fish are abundant.

Cumacea : an order of the Malacostraca, including Diastylis. The eyes are sessile, close together, or fused into one. They are always poorly developed and occasionally are wanting.

Cuticle (L. cuticula, the thin outer layer of the skin) : the most superficial layer of an epithelial sheet, which is either secreted by the epithelial cells or formed by degeneration of the most superficial cells of the epidermis. It may be impregnated with lime salts or chitin.

Cyathaspis (Gr. kuathos, cup ; aspis, shield) : an extinct Pteraspid fish belonging to the class Ostracodermi, characterized by a bowl or cup-like headshield.

Cyclops (Gr. cyclops, the mythical one-eyed giants described by Homer : literally round-eyed) : the water-flea or Daphnia, in which the paired lateral eyes have fused into a single organ.

Cyclostomata (Gr. kuklos, circle ; stoma, mouth) : a primitive class of fishes, characterized by their round mouths and absence of jaws, including the lampreys and hag-fishes.


Decapoda (Gr. deka, ten ; podes, feet) : the division of Crustacea, which have ten walking feet ; and also the family of cuttle-fishes which possess ten " arms " or head-processes arising from the " foot " and surrounding the mouth.

Deric (Gr. deros, skin) : a term used to denote a layer derived from the derma or corium, i.e. mesodermal in origin, as contrasted with ectodermal.

Derma (Gr. derma, skin) : a term usually applied to denote the deeper layer of the skin, or corium.

Dibranchiata (Gr. dis, twice ; branchia, gill) : a subclass of the Cephalopoda characterized by the presence of two gills or ctenidia. The foot is subdivided into eight or ten arms, which surround the mouth. The subclass includes the cuttle-fishes, squids, spirula, and the extinct belemnites.

Dicynodontia (Gr. dis, twice ; kuon, dog ; odous, tooth) : an extinct order of reptiles having two large teeth in the upper jaw, which resemble the " canine " teeth of a dog.

Dinichthys (Gr. deinos, strange, terrible ; ichthus, fish) : an extinct genus of fishes belonging to the order Arthrodira.

Dinophilus T^niatus (Gr. dinos, whirling movement or eddy ; philos, fond ; tainia, band) : a cylindrical worm-like animal characterized by a series of circular ciliated bands, an apical plate, and paired ocelli, belonging to the phylum Trochelminthes.

Diplostichous (Gr. diploos, double ; stichos, layer) : a term applied to an eye consisting of two layers of cells, e.g. the central eyes of Limulus, in which a single layer of hypoderm or vitreous cells lies in front of the retina.

Dipnoi (Gr. dis, twice ; pnoe, breath) : the order of fishes comprising Ceratodus Lepidosiren and Protopterus, commonly known as lung-fishes or mudfishes. Their respiration is aquatic, by means of gills, and aerial by a single sacculated lung, corresponding to the air-bladder of Ganoids and Teleosts.

Diprosopus (Gr. diprosopos, two-faced) : a double-faced monster, as in Duplicitas anterior.

Diptera (Gr. dis, twice ; pteron, wing) : an order of the Insecta having a single pair of transparent membranous wings, e.g. bugs, plant lice.

Dorsal sac : the recess which lies between the velum transversum in front and the superior or habenular commissure behind. Its roof forms the post- velar arch.

Dytiscus marginalis (Gr. dutes, diver ; dutikos, fond of diving) : a carnivorous water beetle belonging to the group Hydradephaga.

Echidna (Gr. echidna, adder ; monster) : the spiny ant-eater of Australia, belonging to the order Monotremata, comprising the egg-laying mammals.

Ectoderm (Gr. ektos, outside ; derma, skin) : the outer layer of cells in a multicellular animal. It corresponds to the term " epiblast " of the growing embryo, and gives rise to the epidermis of the adult animal.

Ectoparietal-eye (Gr. ektos, outside ; L. paries, wall) : the term applied by Patten to " the outer of the two vesicles produced by constriction of


the single terminal vesicle of the parietal organ of vertebrates." He believed that it contains in its walls two of the four retinal placodes, belonging to the undivided terminal vesicle. It corresponds to the parietal eye of Petromyzon (Studnicka).

Edriophthalmata (Gr. hedraios, sitting ; ophthalmos, eye) : a division of the Crustacea having sessile eyes, not supported on a stalk. It includes the Amphipoda, e.g. sandhopper (Talitrus), and Isopoda, e.g. fresh-water shrimp (Gammariis).

Elasmobranchii (Gr. elasma, plate ; branchia, gill) : an order of fishes including the sharks and rays, having plate-like gills.

Endochrome Cells (Gr. endon, within ; chroma, colour) : pigmented cells of the retina in which the pigment granules are deposited in the epithelial cells composing the retina. The pigment may be deposited in one part of a sensory or visual cell or in a specialized epithelial pigment cell.

Endocrine (Gr. endon, within ; krind, separate) : adjective used to denote the function of internal secretion.

Endoparietal eye (Gr. endon, within ; L. paries, wall) : term applied by Patten to " the inner of the two vesicles produced by constriction of the terminal vesicle of the parietal organ of vertebrates." He believed that it contains in its walls two of the four retinal placodes belonging to the undivided terminal vesicle. It corresponds to the " parapineal organ " of Petromyzon (Studnicka).

Endothelium (Gr. endon, within ; thele, nipple) : a layer of cells lining a vessel or vascular space, or the epithelial lining of a serous membrane.

Entoderm (Gr. entos, within ; derma, skin) : the inner layer of embryonic cells, also called endoderm and hypoblast.

Entomostraca (Gr. entomos, incision, division ; ostrakon, shell) : a sub-class of the Crustacea in which the shell is divided into segments. It comprises the orders Phyllopoda, Cladocera, Ostracoda, Copepoda.

Entomostracan eye : the name given to the median eye-spot which is commonly found in species belonging to the four orders which are included in the subclass Entomostraca. It usually consists of three single eyes joined into a triple eye, one segment of which is median and ventral, the remaining segments being lateral and dorsal. The median segment appears to be formed by the fusion of two primarily bilatera' eyes.

Epiblast (Gr. epi, upon ; blastos, germ) : the outer or upper layer of cells in the embryo. See Ectoderm.

Epiphysis cerebri (Gr. epi, upon ; phusis, originate or grow from) : the diverticulum from the roof of the diencephalon, which gives rise to the pineal body, pineal sac, or parietal sense-organ.

Epithelium (Gr. epi, upon ; thele, nipple) : a layer of cells covering a surface or lining a duct, canal, or vessel. It covers the nipple-shaped dermal papilla; of the skin.

Epizoa (Gr. epi, upon ; zoon, animal) : (i) animals which are parasitic on other animals ; (2) a subclass of the crustaceans in which the adult animal is usually fixed to the gills or exterior of a fish or other animal. The


young are free-swimming, and are provided with eyes and antennas : e.g. Argulus.

Eryops : a genus of extinct amphibia belonging to the order Stegocephala.

Eucone eyes (Gr. eu, well, complete ; konos, cone) : invertebrate eyes in which the crystalline cones are well developed, as in many of the compound eyes of Crustacea.

Euphausia pellucida (Gr. eu, well ; phausis, bright ; L. pelhicidus, clear, transparent) : an order of the Eucarida. The carapace coalesces with the thoracic segments to form a continuous shield and there are stalked eyes.

Eurypterus (Gr. eurus, wide ; pteron, wing) : an extinct scorpion-like genus belonging to the order Merostoma.

Exochrome cells (Gr. ex, out of; chroma, colour) : pigment cells of the retina of extraneous origin, and thought to be derived from the subepidermal connective tissue.

Flabellum (L. flabelhim, fan) : the last appendage of the prosoma of the adult Limulus has an outer segment which is called the epipodite or flabellum.

Fluke : an internal parasitic worm of leaf-like form (Distoma hepaticum) belonging to the class Trematoda. It is frequently found in the gall bladder or bile ducts of the sheep.

Fundulus heteroclitus (L. fundulus, closed end of gut, or tube ; Gr. heteroclitos, irregularly bent) : a marine minnow, the developing embryos of which were used by Stockard and others for the experimental production of cyclops and other deformities.

Fuscin (L. foscus, brown) : the colouring material contained in the pigment granules of the hexagonal cells of the retina, a form of melanin.

Galeodes : an Arachnid belonging to the order Solpugidae, and resembling the scorpions.

Gammarus ornatus : the gadfly, belonging to the order Hymenoptera of the class Insecta. A small median or frontal ocellus is situated between two large faceted eyes.

Ganoid (Gr. ganos, sheen ; eidos, like) : (1) A term applied to the glistening scales or plates of certain fishes ; they are composed of a deep layer of true bone, which is covered by a superficial layer of enamel or ganoin. (2) An order of fishes characterized by incomplete ossification of the endoskeleton, and an exoskeleton usually formed of rhombic, ganoid plates, e.g. Polypterus ; Osteolepis, a primitive extinct genus.

Gasteropoda (Gr. gaster, stomach ; pous, foot) : the class of Mollusca, comprising univalve forms in which movement is effected by contractions of the foot — e.g. snails and slugs.

Gastrula (Gr. gaster, stomach) : the name applied to the double-layered vesicle formed by the invagination of one part of the wall of the blastocyst into the opposite part.

Glabella (L. glabella, smooth, bare area) : e.g. the smooth median part of the cephalic-shield of a trilobite.

Gnathostomata (Gr. gnathos, jaw ; stoma, mouth) : the Branch of fishes characterized by the presence of jaws in the mouth, as contrasted with the cyclostomata in which jaws are absent.


Gymnophiona (Gr. gumnos, naked ; ophis, snake) : an order of the Amphibia

comprising the snake-like Caecilia. Gymnotus (Gr. gumnotes, naked) : the electric eel of South America. Gyrinid^e. (Gr. gureud, run in a circle) : a family of beetles which possess two

pairs of compound eyes. See Bibionida. Hatteria punctata or Sphenodon, a primitive type of reptile belonging to

the order Rhynchocephalia, in which the parietal eye is well developed. Helix nemoralis (Gr. helix, twisted or coiled) : land-snail, belonging to the

order Pulmonata of the Mollusca. The eyes are situated at the apex

of each posterior or ocular tentacle. Hemiaspida (Gr. hemi, half; ajpis, shield) : an extinct Palaeozoic order related

to the Xiphosura, and including Bunodes, Hemiaspis, and Belinurus. Hemichorda (Gr. hemi, half ; chorde, string) : a subphylum of the chordata,

comprising Balanoglossus. An oesophageal diverticulum in the region

of the neck is regarded as a rudiment of the notochord. The tornaria,

or larva, has an apical plate bearing two eye-spots. Hemiptera (Gr. hemi, half; pteron, wing) : an order of the Insecta in which

the anterior wings are membranous at the tip, while the inner part is

chitinous — e.g. bugs, plant lice, cicadas, lice {Anoplura), wingless

parasites of mammals. Hexapoda (Gr. hexa, six ; pous, foot) : name applied to the Insecta on account

of their having six legs. Hirudinea (L. hirudo, leech) : the order of Annelida, which includes the

leeches. Holocephali (Gr. holos, whole ; kephale, head) : a sub-order of the Elasmo branchs which includes Chimcera and Callorhynchus. Holochroal eyes (Gr. holos, complete ; chroa, surface) : the term used to

denote a form of compound lateral eye of trilobites, in which the corneal

surface was continuous ; the ommatidia not being separated as in the

schizochroal type. Holostomata (Gr. holos, whole ; stoma, mouth) : a division of the gasteropod

molluscs in which the opening of the spiral shell is entire. Homarus : lobster belonging to the order Decapoda, of the class Crustacea. Hoplocarida (Gr. hoplon, armour ; karis, a small lobster) : a division of the

Crustacea, comprising the squills, in which the carapace or head-shield

covers only the anterior thoracic segments. Large stalked eyes are

borne by the first segment of the anterior region of the head. Hydrodroma (Gr. hudra, water ; dromos, movement, running) : a fresh-water

mite belonging to the family Hydrachnidae and the order Acarina. It has

two paired eyes and a central or median eye. Hymenoptera (Gr. humeri, membrane ; pteron, wing) : an order of the Insecta

characterized by having four membranous wings, e.g. bee, wasp, ant. Hypodermis (Gr. hupo, under ; derma, skin) : the single layer of cells which

lies beneath the cuticle in invertebrates. It is also known, with reference

to invertebrate eyes, as the vitreous or corneagen layer. It corresponds

to the deeper cells of the epidermis of vertebrates and the tall columnar

cells composing it are spoken of as palisade or epiderm cells.


Hypostome (Gr. hupo, under ; stoma, mouth) : the upper lip or " labrum" of certain Crustacea, e.g. Trilobita.

Ichthyopsida (Gr. ichthus, fish ; opsis, appearance) : the division of vertebrata which comprises the fishes and amphibia ; also known as branchiate vertebrates.

Ichthyopterygia (Gr. ichthus, fish ; pterux, wing or fin) : an extinct order offish-like reptiles, which includes the Ichthyosauri.

Ichthyosaurus (Gr. ichthus, fish ; saura, lizard) : an extinct order of reptiles belonging to the Mesozoic period.

Isopoda (Gr. isos, equal ; pous, foot) : an order of the Crustacea in which the feet are approximately equal in size and appearance, e.g. Asellus, Sphceroma. The eyes are compound and usually sessile ; in some examples, however, they consist of a collection of simple eyes.

Jurassic System or Period : the oolitic and lias deposits found in the Jura Mountains and stretching across England from Yorkshire to Dorset. It belongs to the Mesozoic period and contains remains of marine animals such as the ammonites and large Saurian reptiles.

Kainozoic (Gr. kainos, recent ; zoe, life) : the tertiary period in geology, in which the remains of animals and plants closely resemble living species.

Kiaeraspis (Gr. apis, shield) : a primitive Palaeozoic fish belonging to the Order Cephalaspidomorphi of the branch Ostracodermi.

King-crab (Limulus) : a marine arachnid belonging to the order Xiphosura. It is characterized by a large dorsal-shield and plate-like " book gills."

Labium (L. lip) : term used to denote the lower lip of articulate animals. See Labrum.

Labrum (L. lip) : term used to denote the upper lip of articulate animals.

Labyrinthodontia (Gr. laburinthos, labyrinth ; odous, tooth) : an extinct order of the Amphibia, also named Stegocephala. The term was employed to express the complicated structural appearance of the teeth when seen in transverse section.

Lamellibranch (L. lamella, plate ; Gr. branchia, gill) : a bivalve mollusc having lamellar gills, e.g. Fresh-water mussel (Anodonta cygnea) : scallop (Pecteri). In some, the larva of which lead a parasitic existence, visual sense-organs are vestigial or absent. In others, e.g. Pecten, highly differentiated eyes are developed in the adult animal round the edge of the mantle.

Lens (L. lens, lentis, lentil) : the crystalline lens of the eye, so named on account of its being about the size and shape of a lentil seed. There are three principal types of lens, named according to their composition : cuticular, vitreous, cellular. In some instances two or all three of the constituent elements may be combined in the formation of a single lens. Lepas fascicularis, Lepas anatifera (L. lepas, small shell-fish) : cirripede Crustacea, e.g. barnacle, characterized by the fixed condition of the adult animal and by passing through a free-swimming nauplius stage, which is followed by a cypris stage in which the larva is enclosed in a bivalved shell and has both simple (ocellar) and compound eyes.


Lepidoptera (Gr. lepis, scale ; pteron, wing) : an order of the Insecta having four wings covered with scales, e.g. butterflies, moths.

Lepidosiren (Gr. lepis, scale ; surinx, tube) : a genus of the lung-fishes (Dipnoi) of a long pipe-like form, found in South America.

Lepidosteus (Gr. lepis, scale ; osteon, bone) : genus of ganoid fishes, e.g. gar-pike.

Lepidurus (Gr. lepis, scale ; oarus, tail) : a crustacean belonging to the subclass Branchiopoda and order Notostraca. It has a well-developed head shield and a tail-like plate between two caudal styles.

Lingula (L. variant of ligula, spatula or shoe-string) : lamp-shell, a stalked brachiopod in which the two valves of the shell are not joined by a hinge. Existing genera of Lingula appear first in the lower Cambrian rocks, and with other genera of the Brachiopoda, e.g. Cistella, it forms a striking example of persistence of type. See Cistella and Rhynchonella.

Malacostraca (Gr. malakos, soft ; ostrakon, shell) : a subclass of the Crustacea characterized by having a soft shell, e.g. the shrimps and prawns.

Mantle : the outer covering or pallium which protects the viscera in most of the Mollusca.

Marsipobranch (Gr. marsipos, pouch ; branchia, gill) : the order of cyclostome fishes, which includes the lampreys and hag-fishes, which is characterized by pouch-like diverticula separated by septa bearing gills.

Melanoblast (Gr. melas, black ; blastos, bud or germ) : branched pigment cells of the epidermis. They are believed to elaborate pigment granules which pass from them into the epidermal cells.

Melanophore (Gr. melas, pigment ; phoreo, bear) : a cell bearing pigment granules, also called chromatophore.

Merostomata (Gr. meros, thigh ; stoma, mouth) : an extinct order of the Crustacea, including the extinct forms Eurypterus and Pterygotus and the living genus Limulus. The appendages situated round the mouth act as jaws, and their free extremities serve as legs or as prehensile organs. The head-shield bears two lateral compound eyes and two ocelli placed near the median line.

Molluscoida (L. mollis, soft ; mollesco, become soft ; Gr. eidos, likeness) : a subdivision of invertebrates resembling the Mollusca in possessing soft bodies, including the Polyzoa, Brachiopoda, and Phoronida.

Monostichous (Gr. monos, single ; stichos, layer) : a term applied to an eye consisting of a single layer of cells, e.g. the larval eye of Dytiscus or lateral eyes of Limulus.

Myriapoda (Gr. murios, numerous, 10,000 ; podes, feet) : a class of the Arthropoda comprising the centipedes and millipedes.

Nauplius (L. nauplius, a sea-fish) : the free-swimming larva which results from the hatching of the embryo of certain crustaceans, e.g. Apus.

Nautilus (Gr. nautilos, sailor) : a genus of the subclass Tetrabranchiata of the class Cephalopoda. It is a primitive type of mollusc the shell of which resembles the extinct Ammonites.

Nereis : A marine annelid belonging to the subclass Polychaeta. It has two pairs of eyes of a simple ocellar type.


Neuroptera (Gr. neuron, nerve, cord ; pteron, wing) : an order of the Insecta having four membranous wings, strengthened by tendinous cords or " nervures," e.g. dragon-flies.

Notostraca (Gr. notos, back ; ostrakon, shell) : an order of the branchiopod crustaceans comprising Apus and Lepidurus, so named on account of the shell-like carapace which covers the dorsal surface of the head and thorax.

Nyctiphanes (Gr. nuctiphanes, visible by night) : a crustacean belonging to the order Euphausiacea, having luminous organs or photospheria on the basal joints of certain of the thoracic feet.

Ocellus (L. diminutive of oculus) : the name given to a single or simple eye as contrasted with a multiple or aggregate eye. The ocellus may be a simple placode or eye-spot ; an optic pit, with open mouth ; or a closed vesicle, having a corneagen or vitreous lens. In some cases a group of larval ocelli are replaced in the adult insect (imago) by an aggregate or compound eye.

Ommatidium (Gr. omma, eye, diminutive suffix) : one of the component units of an aggregate or compound eye of an adult arthropod, e.g. Dytiscus marginalis. Each ommatidium consists of an outer dioptric part, formed of the vitreous cells or crystalline-cones, and an inner percipient part called the retinula, which is composed of a central visual-rod or rhabdome, and the neuro-sensory cells. The retinula; are separated by inter-retinular pigment cells.

Oniscus : wood louse, a crustacean belonging to the order Isopoda. They resemble the trilobites in being able to roll themselves up into a ball, and in the feet being like one another and approximately equal in size.

Ontogeny (Gr. on, ontos, a being or individual ; genesis, origin) : the lifehistory of an individual, including embryonic development.

Ordovician System or Period : the geological strata between the Silurian and Cambrian found in Bala, Llandello, and Scotland. It contains remains of marine invertebrates, e.g. small ostracode Crustacea.

Osteolepis (Gr. osteon, bone ; lepis, scale) : an extinct Ganoid fish having a protective covering of closely set bony scales, and a large pineal foramen situated in a single frontal bone. See Lepidosteus.

Ostracoda (Gr. ostrakon, shell) : an order of small bivalve Crustacea, including Cypris, in which median and sometimes both median and lateral eyes are present.

Paltemon : prawn, belonging to the subclass Malacostraca, or soft-shelled crustaceans.

Palisade cells (Fr. palissade, enclose with fence) : the name given to the tall columnar cells which form a single layer of cells beneath the cuticle in many invertebrate animals. They are also termed " hypoderm cells."

Paraphysis (Gr. para, beside ; phusis, growth) : a branched tubular outgrowth from the roof of the third ventricle. It lies in front of the epiphysis and the postvelar arch or dorsal sac. It is well-developed in Sphenodon and certain fishes.


Parapineal organ (Gr. para, beside ; L. pinus, fir cone) : the anterior or left parietal sense-organ of Petromyzon. It lies beneath the right parietal sense-organ and is smaller and less differentiated than the right organ.

Parietal (L. paries, wall) :

bone: roof-bone of skull.

eye : visual sense-organ.

" fleck " : white spot visible through cornea.

foramen : complete parietal canal.

pit : incomplete parietal canal.

plate : separate bone in pineal region.

" plug " : translucent tissue closing up pineal canal.

region : pineal region of roof of third ventricle.

scale : horny scale overlying pineal region of skull.

sense-organ : terminal sensory-vesicle.

vesicle : dilated distal end of pineal stalk.

Patella (L. Patella, a small pan or dish) : the limpet, a gasteropod mollusc having a low conical shell. The paired eyes of the adult animal are open pits, without a lens. The larva is a typical free-swimming trochophore.

Peripatus (Gr. peripateo, walk about) : an aberrant arthropod resembling a caterpillar ; neither body nor legs are definitely segmented. The eyes are of a simple ocellar type, and resemble those of Nereis.

Permian System or Period : the uppermost strata of the Palaeozoic or Primary Era — found in the district of Perm, East Russia. It consists of sandstone, marls, rocky salt, and magnesium limestone ; the conditions were chiefly continental and desert.

Phascolosoma (Gr. phaskolos, leather bag or purse ; soma, body) : a genus of the suborder Sipunculidae, class Annulosa. Eyes are absent in the adult animal ; a pair of ocelli are, however, present in the trochophore larva.

Phyllopoda (Gr. phullon, leaf ; pous, foot) : an order of the Crustacea having leaf-like legs and comprising Apus, Lepidurus, and the fairy-shrimp or Branchipus diaphanus. The order resembles in many respects the extinct Trilobita.

Phylogeny (Gr. phulon, race ; genesis, origin) : the ancestral origin of a phylum or subdivision of a phylum.

Pineal body (L. pinus, a fir cone) : the epiphysis cerebri, so named on account of its conical shape in man and certain animals.

Pineal foramen : the canal which contains the pineal organ ; it is usually situated between the parietal bones or in the centre of a single bone formed by fusion of the parietal bones. It may, however, be situated between the two frontals, in a single frontal bone or in a special pineal plate.

Pineal sac : the dilated distal end of the " epiphysis," sometimes termed the end-vesicle. It is well developed in Sphenodon, contains pigment, and it was believed by Dendy to represent the right member of a pair of parietal sense-organs of which the left, or pineal eye, is more highly developed and lies in the parietal foramen.


Pineal system (L. pinus, a fir cone) : the term applied to the parietal senseorgan (or organs) and the associated structures, such as the parapineal organ, pineal sac, the pineal stalk, the epiphysis, the pineal nerves, commissures, and habenular ganglia.

Planaria (L. planus, flat) : a small flat worm, showing bilateral symmetry and having paired ocelli. Phylum Plathelminthes.

Podophthalmata (Gr. pons, foot ; ophthalmos, eye) : a division of the Crustacea having compound eyes borne at the free ends of movable stalks. It comprises two Orders, Stomatopoda (e.g. Squilla) and Decapoda (e.g. Astacus).

Polyclada (Gr. polus, many ; dados, branch) : an order of the flat worms belonging to the class Turbellaria, so named on account of the complex branching of the intestine.

Polyphemus (Gr. the cyclopean giant described by Homer) : a small crustacean belonging to the order Cladocera, in which the eyes are sessile and are joined into a single organ.

Porthetis spinosa (Gr. porthetes, destroyer ; L. spinosa, thorny) : an insect belonging to the group Acridiidae, in which there is a coexistence of the compound and simple eyes in the imago. The three frontal ocelli are arranged in a triangle, one in front, two behind.

Pterichthys (Pterychthys) (Gr. pteron (pterux), wing ; ichthus, fish) : an extinct fish belonging to the order Antiarchi of the class Ostracodermi. It is characterized by wing-like pectoral fins.

Pterygotus (Gr. pterux, wing ; ous, ear) : a genus of the Eurypterida belonging to the order Merostomata. The antennae ended in prehensile lobsterlike claws ; the maxillipedes formed large ear or oar-like appendages which could be used as paddles.

Retinula (L. diminutive of rete, net) : the inner sensitive segments of the ommatidia of an aggregate or compound eye, as contrasted with the outer, purely dioptric part. Some writers include the pigment cells, which surround the clear cells of the rhabdome, whereas others appear to limit the term to the clear central cells of the ommatidium.

Rhabdite (Gr. rhabdion, a little rod) : the central columnar cell of a retinula. The basal part of the cell containing the nucleus is usually expanded, whereas the distal part tapers or is prolonged as a slender refractile rod.

Rhabdome (Gr. rhabdos, rod) : the central clear cells of a retinula, including the rhabdite and the peripheral non-pigmented cells.

Rhabdomere (Gr. rhabdos, wand or rod ; meros, part) : one of the constituent cells or rods of a rhabdome.

Rhipidoglossa (Gr. rhipis, a fan, something thrown out, as a javelin ; glossa, tongue) : the name given to the chameleon family on account of the rapid movement of the long tongue, which is used for catching flies.

Rhynchonella (Gr. diminutive of rhunchos, a small beak) : an articulate brachiopod in which the dorsal and ventral valves of the shell are joined by a horizontal hinge with a beaked process. Found in lower cretaceous strata, and closely resembles the shells of certain living species.


Romberg's sign : if the patient closes his eyes when standing with the feet together, he sways from side to side, and if not supported will eventually fall. It occurs in cases, such as locomotor ataxia, in which there is a loss of the deep reflexes, which are concerned in maintaining the erect posture. Salpa (L. salpa, stock-fish) : a tunicate belonging to the order Thaliacea. A median horseshoe-shaped eye is present, and sometimes small accessory eyes. Sauria (Gr. saura, lizard) : term applied to lizard-like reptiles in general, but

sometimes restricted to the crocodiles and Lacertilia. Sauropsida (Gr. saura, lizard ; opsis, appearance) : the name given collectively

to the two classes Birds and Reptiles. Schizochroal eyes (Gr. schizo, cleave, separate ; chroa, surface) : the term applied to the type of lateral compound eye of trilobites in which the constituent units of the eye were separate, the areas between the corneal facets being occupied by an interstitial test or sclera. Sepia (L. sepia, cuttle-fish) : a mollusc belonging to the class Cephalopoda possessing ten arms or feet and highly developed eyes. The name " sepia " is also used for the black pigment which is obtained from it. Stemma (Gr. stemma, crown or wreath) : the simple eyes or ocelli of certain

invertebrates, e.g. the frontal stemmata of insects. Tapetum (Gr. tape, L. tapetum, carpet, many-coloured garment or tapestry) : T. argentea, the silvery or greenish-gold, iridescent membrane between the lamina fusca and choroid coat in certain Teleost fishes. The iridescence is due to crystals of calcium salts deposited in the cells : syn. T. cellulosum. T. pellucidum, a delicate fibrous membrane in the choroid coat next the retina. It has a metallic lustre due to the reflection and interference of light rays by the fibrillar in the membrane. It is found in certain fishes, carnivores, and ungulates, e.g. the horse and ox. Reflecting membranes behind or external to the retina are also found in some invertebrate eyes and luminous organs, e.g. the photospheria, found on the first abdominal segments of Nyctiphanes. Tetrabranchiata (Gr. tetra, four ; branchia, gills) : a subclass of the Cephalopoda, having four comb-like gills or ctenidia. It includes one living genus, Nautilus, and the extinct Ammonites are usually referred to it. Tretaspis (Gr. tretos, perforated ; aspis, shield) : the name given to the larval form of a genus of the trilobites characterized by " holes " or eye-spots on the glabellum. Triassic System or Period : the lowest strata of the Mesozoic period, during which mammal-like reptiles first made their appearance. It comprised the Rhoetic, Keuper, and Bunter series. Trilobita (Gr. treis, three ; lobes, lobe) : an extinct Order of crustaceans. The dorsal aspect is divided into three lobes, a median or axial and lateral or pleural. In many the labrum or hypostome supports a pair of compound eyes ; and a median eye-tubercle is present in the larval fossils of certain forms, e.g. Trinucleus.


Triplostichous (Gr. triploos, threefold ; stichos, layer) : an eye consisting of three layers : preretinal, retinal, and postretinal, e.g. the median eyes of the larval scorpion, in which the retina is inverted. The post-retinal layer may be pigmented or serve as a reflecting membrane (tapetum lucidum or argentea). Triton : a marine gastropod mollusc enclosed in a univalve spiral shell, and possessing two simple eyes of the upright type situated near the bases of the tentacles. Trochelminthes (Gr. trochos, wheel ; helmins, worm) : an invertebrate phylum comprising the wheel animalcules or rotifers. The free-swimming larva is known as a trochosphere or trochophore. Trochophore (Gr. trochos, wheel ; phoreo, bear or carry) : the cylindrical, free-swimming larva of certain annelids and molluscs. It is characterized by two or more circlets of cilia, resembling those of the rotifers, and the presence of an apical plate bearing an upright tuft of cilia, and often two ocelli. Tunicata (L. tunica, cloak) : a subphylum Urochordata, which includes the ascidians or sea-squirts, so named on account of the thick, leathery coat with which they are covered. Turbellaria (L. turbo, disturb) : a class of flat worms, mostly leaf-like in form, including the Planaria. Pigmented eye-spots are found on the dorsal aspect of the head-region. Urochorda (Gr. our a, tail ; chorde, string) : a subphylum of the Chordata, in which a notochord limited to the tail region is present in the freeswimming larva. Urodela (Gr. oura, tail ; delos, visible) : tailed amphibians, including the newts and Proteus anguineus.

Varanus : a lizard of the Monitor family in which the parietal sense-organ is large and well differentiated.

Veliger (L. velum, a sail ; gero, carry) : a stage in the development of certain Gasteropods, e.g. Vermetus. The preoral circlet of the trochophore larva has become bilobed, and by means of its cilia serves as an organ of locomotion. Paired lateral eyes are present at the bases of the tentacles. The term is also applied to one stage in the development of Geotria.

Velum transversum (L. velum, veil or curtain) : the thin fold of the roof of the third ventricle, which forms the anterior boundary of the dorsal sac. Laterally it is continuous with the choroid plexuses of the lateral ventricles.

Yungia : a marine Planarian belonging to the order Polycladidas, class Turbellaria, of the flat- worms. Ocelli are developed over the region of the apical cells of the free-swimming larva.

Zcea (Gr. zoon, living being, animal) : a larval stage of the crab, characterized by the very large size of the compound eyes as compared with the size of the body.

   The Pineal Organ (1940): 1 Introduction | 2 Historical Sketch | 3 Types of Vertebrate and Invertebrate Eyes | Eyes of Invertebrates: 4 Coelenterates | 5 Flat worms | 6 Round worms | 7 Rotifers | 8 Molluscoida | 9 Echinoderms | 10 Annulata | 11 Arthropods | 12 Molluscs | 13 Eyes of Types which are intermediate between Vertebrates and Invertebrates | 14 Hemichorda | 15 Urochorda | 16 Cephalochorda | The Pineal System of Vertebrates: 17 Cyclostomes | 18 Fishes | 19 Amphibians | 20 Reptiles | 21 Birds | 22 Mammals | 23 Geological Evidence of Median Eyes in Vertebrates and Invertebrates | 24 Relation of the Median to the Lateral Eyes | The Human Pineal Organ : 25 Development and Histogenesis | 26 Structure of the Adult Organ | 27 Position and Anatomical Relations of the Adult Pineal Organ | 28 Function of the Pineal Body | 29 Pathology of Pineal Tumours | 30 Symptomatology and Diagnosis of Pineal Tumours | 31 Treatment, including the Surgical Approach to the Pineal Organ, and its Removal: Operative Technique | 32 Clinical Cases | 33 General Conclusions | Glossary | Bibliography
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