Text-Book of Embryology 2-11 (1919) - Revision history

Z8600021: /* Myxinoids */

2018-06-26T08:28:57Z

Myxinoids

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	period and the young born in an		period and the young born in an advanced stage [Notidam/us, Mustalus, Galeus, Uarcharias, Zygaena, Lamna, Alopias, Uetorlzxinus, Acumtlmlas, Scymnus, Squatina, Torpedo, Trygonidae,Myliobatidae]. Amongst the viviparous Elasmobranchs preserved developmental stages of Torpedo (Fig. 247) may be obtained from Naples, and of Acanthias from various marine laboratories.

	~~advanced stage [Notidam/us, Mus—'~~

	~~talus, Galeus, Uarcharias, Zygaena, Lamna, Alopias, Uetorlzxinus, Acumtlmlas, Scymnus, Squatina, Torpedo, Trygonidae,Myliobatidae].~~ Amongst the ~~viviparous Elasmobranchs preserved developmental stages~~ of ~~Torpedo~~ (~~Fig. 247~~) ~~may~~ be obtained from ~~Naples~~, ~~and~~ of ~~Acanthias~~ from ~~various marine laboratories~~.		Amongst the oviparous forms certain species of Skate (Rania) are used as food-ﬁshes and their eggs can frequently be obtained in quantity at trawling centres. In such cases arrangements can be made with local ﬁsh-dealers to send on by post the “ skate-purses ” taken from the oviducts when the ﬁsh are cut up.‘ The eggs of the different species differ in size and in the characters of the shellshape, colour, degree of translucency (Williamson, 1913). Of the European species B. batvls is the most convenient species to use; the normal period of spawning is from December to April but the retarding effect of the low temperature i.s so great that December eggs are practically overtaken in their development by the April eggs. The complete period of development is roughly 20 months, most of the eggs hatching about August.

	Amongst the oviparous forms certain species of Skate (Rania) are used as food-ﬁshes and their eggs can frequently be obtained in quantity at trawling centres. In such cases arrangements can be made with local ﬁsh-dealers to send on by post the “ skate-purses ” taken from the oviducts when the ﬁsh are cut up.‘ The eggs of the different species differ in size and in the characters of the shellshape, colour, degree of translucency (Williamson, 1913). Of the European species B. batvls is the most convenient species to use; the normal period of spawning is from December to April but the retarding effect of the low temperature i.s so great that December eggs are practically overtaken in their development by the April eggs. The complete period of development is roughly 20 months, most of the eggs hatching about August.

	The eggs should be posted in damp seaweed. On arrival the soft sticky marginal zone of the shell, which separates off except at		The eggs should be posted in damp seaweed. On arrival the soft sticky marginal zone of the shell, which separates off except at
			one end and serves to anchor the egg to the sea-bottom, is removed, and the date is marked in ink with a wooden style upon the flat portion of shell between the two horns.

	~~one end and serves to anchor the.~~

	~~egg to~~ the ~~sea-bottom, is removed, and the date is marked in ink with~~ a ~~wooden style upon the flat portion of~~ shell ~~between the two horns~~.		1 Jamieson observed out of many thousands of eggs only one case of the inclusion of two eggs within a common shell.

	~~3 —u-: t ‘~~
	~~1 Jamieson observed out of many thousa.°nds of eggs only one case of the inclusion of two eggs within a common shell.~~

			For hatching boxes it is convenient to take ordinary ﬁsh boxes freely perforated with anger holes, provided with a cross partition in the centre, and pitched inside and out to discourage the growth of seaweeds. The hatching boxes are moored aﬂoat in pure sea-water within a breakwater or other shelter. About 20 eggs are placed in each compartment.

	For hatching boxes it is convenient to take ordinary ﬁsh boxes freely perforated with anger holes, provided with a cross partition in the centre, and pitched inside and out to discourage the growth of seaweeds. The hatching boxes are moored aﬂoat in pure sea-water within a breakwater or other shelter. About 20 eggs are placed in each compartment.

	On alternate days the boxes are drawn a few times backwards and forwards through the water to dislodge any sediment that may have accumulated. Once a week they are hauled’out of the water and each egg-shell tested by rubbing the ﬁnger over its surface. If a slippery mucus-like layer has developed on its surface the egg is useless and should be got rid of.		On alternate days the boxes are drawn a few times backwards and forwards through the water to dislodge any sediment that may have accumulated. Once a week they are hauled’out of the water and each egg-shell tested by rubbing the ﬁnger over its surface. If a slippery mucus-like layer has developed on its surface the egg is useless and should be got rid of.


	When the egg has reached the desired period of development it is removed from the Water, placed in a horizontal position with the more strongly convex side below and opened by carefully removing the greater part of the less convex side of the shell. The isolated piece of shell must be lifted off very carefully as the albumen is very adhesive and the vitelline membrane extremely delicate.		When the egg has reached the desired period of development it is removed from the Water, placed in a horizontal position with the more strongly convex side below and opened by carefully removing the greater part of the less convex side of the shell. The isolated piece of shell must be lifted off very carefully as the albumen is very adhesive and the vitelline membrane extremely delicate.


	In the early stages the embryo is almost invisible in the fresh state so the egg, still held carefully in a horizontal position, is gently submerged in ﬁxing ﬂuid. The blastoderm then comes into view and after a short time may be excised and ﬂoated into a watch-glass to complete ﬁxation and the subsequent processes.		In the early stages the embryo is almost invisible in the fresh state so the egg, still held carefully in a horizontal position, is gently submerged in ﬁxing ﬂuid. The blastoderm then comes into view and after a short time may be excised and ﬂoated into a watch-glass to complete ﬁxation and the subsequent processes.


	In later stages (Fig. 248) where the body of the embryo is constricted off from the yolk—sac, it is narcotized by submersion in sea-water containing alcohol and then the yolk-stalk is ligatured with thread and the embryo excised for further treatment.		In later stages (Fig. 248) where the body of the embryo is constricted off from the yolk—sac, it is narcotized by submersion in sea-water containing alcohol and then the yolk-stalk is ligatured with thread and the embryo excised for further treatment.


	Embryological material of the Sharks is to be preferred to that of the Skates or Rays on account of their less specialized character but unfortunately it is more diﬂicult to obtain in quantity. Small sharks of the genus Scyllelum and allied genera occur commonly round the shores of the various continents and their eggs may be found attached to seaweed at extreme low tides.		Embryological material of the Sharks is to be preferred to that of the Skates or Rays on account of their less specialized character but unfortunately it is more diﬂicult to obtain in quantity. Small sharks of the genus Scyllelum and allied genera occur commonly round the shores of the various continents and their eggs may be found attached to seaweed at extreme low tides.

	On the British coasts a well-known spawning ground for Sag/llium canicula exists at Careg Dion about 2% miles from Beaumaris on the Anglesea side of the Menai Straits in between 3 and 4 fathoms of water and in spots not exposed to strong tidal currents} The eggs are deposited usually in the morning, the shorter stouter pair of ﬁlaments which issue ﬁrst from the cloacal opening being trailed about /amongst tufts of the seaweed Halidrys siliquosa until they become entangled when the ﬁsh swims round so as to wind the elastic ﬁlaments ﬁrmly amongst the seaweed. The eggs can only be obtained at very low and specially favourable spring tides and as White ﬁnds at one time embryos of all stages of development it would appear that oviposition is not limited to any deﬁnite season. ~ Sag/llwlum not infrequently deposits its eggs in aquaria and at the

	1 For the details in regard to this locality I‘ have to thank Professor Philip J. White of Bangor.		On the British coasts a well-known spawning ground for Sag/llium canicula exists at Careg Dion about 2% miles from Beaumaris on the Anglesea side of the Menai Straits in between 3 and 4 fathoms of water and in spots not exposed to strong tidal currents} The eggs are deposited usually in the morning, the shorter stouter pair of ﬁlaments which issue ﬁrst from the cloacal opening being trailed about /amongst tufts of the seaweed Halidrys siliquosa until they become entangled when the ﬁsh swims round so as to wind the elastic ﬁlaments ﬁrmly amongst the seaweed. The eggs can only be obtained at very low and specially favourable spring tides and as White ﬁnds at one time embryos of all stages of development it would appear that oviposition is not limited to any deﬁnite season. ~ Sag/llwlum not infrequently deposits its eggs in aquaria and at the Berlin Aquarium it has been observed that pairs of eggs were deposited at intervals of about ten days. The methods of technique mentioned in connexion with the Skate are also applicable to the eggs of Scyllium.


			1 For the details in regard to this locality I have to thank Professor Philip J. White of Bangor.


	Berlin Aquarium it has been observed that pairs of eggs were deposited at intervals of about ten days. The methods of technique mentioned in connexion with the Skate are also applicable to the eggs of Scyllium.

	It should not be forgotten that, as mentioned earlier in this		It should not be forgotten that, as mentioned earlier in this volume, one of the greatest desiderata in Vertebrate embryology is an oviparous shark with eggs of small size.


	FIG. 248.—Raia batis, embryos.		FIG. 248.—Raia batis, embryos.

	at, atrial portion of heart; E, eye; c, conus ; f.g, foregut; H, heart; l, lens; Zi, liver; ot, otocyst; pin, pineal organ ; rh, thin roof of fourth ventricle; v.c.I, etc., visceral clefts; y.s, yolk-stalk; V, VII, VIII, cranial nerves.		at, atrial portion of heart; E, eye; c, conus ; f.g, foregut; H, heart; l, lens; Zi, liver; ot, otocyst; pin, pineal organ ; rh, thin roof of fourth ventricle; v.c.I, etc., visceral clefts; y.s, yolk-stalk; V, VII, VIII, cranial nerves.

	~~volume, one of the greatest desiderata in Vertebrate embryology is an oviparous shark with eggs of small size. ‘~~

	==Teleostomi==		==Teleostomi==

Z8600021: /* Amphibia */

2018-06-25T03:34:56Z

Amphibia

← Older revision		Revision as of 14:34, 25 Haziran 2018
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	~~Flu~~. .~~_')l.—-~~String of eggs of unknown Frog from the Gambia. Obtalned ahve from Individual variations in the rate of developnu.-nt are indicated animal dealers and hy the varying size of the yolk-plug.		Fig. 251. String of eggs of unknown Frog from the Gambia. Obtalned ahve from Individual variations in the rate of developnu.-nt are indicated animal dealers and hy the varying size of the yolk-plug.

			in these it may be taken as a general rule that breeding takes place at-the commencement of the rainy season, or in other words when environmental conditions become favourable after a prolonged period during which they have been unfavourable. By bear ing this principle in mind such tropical T i amphibians may usually be induced to breed in captivity. Bles in his excellent account of the life-history of Xenopus (1905) describes a method which will be found to be of general use. The pair of animals were kept in a Budgett tropical aquarium consisting of a glass bell-jar 20 inches in diameter dipping into a galvanized iron water-tank heated by a small Bunsen burner and oxygenated by plants of Vallisnemla. During summer the temperature of the water in the belljar was kept at about 25° C. The water was not changed. The frogs were fed daily with small earthworms or thin strips of raw calf’s liver until they would eat no more. In December the temperature was allowed to fall to 15°-16° during the day and as low as 5"-8° during the night. As the temperature rose With the °;lﬁI1:ucca'1wity_M bmmpm_ onset of spring the frogs became more N’ mes, n1c.s'odcrnlsnigincnts. 4, actives Wilkmg “P out of the lethargic condition induced by the winter's cold. Breeding was induced by simulating the natural conditions of the rainy season. The temperature was raised to about 22° 0. Each morning and evening about two gallons of the water was drawn off, allowed to cool for twelve hours and then returned to the aquarium in the form of a fountain of spray from the upturned end of a glass siphon drawn out to a fine point so as to produce the effect of a shower of rain. Within a week or two breeding took place.


			The chief diﬁiculty in the way of cutting sections of Frog’s eggs is due to the presence of the jelly-like envelope. This may be got rid of by prolonged soaking, six months or more, in -5% formalin (Ogushi, 1908), or by ﬁxing in Zenker’s ﬂuid and leaving the efgs 111 this ﬂuid renewing it after 2 to 3 days and continuing the treatment for 8 to 14 days or longer, shaking gently so as to remove the envelopes (Kallius, 1908). '


	in these it may be taken as a general rule that breeding takes place at-the commencement of the rainy season, or in other words when environmental conditions become favourable after a prolonged period during which they have been unfavourable. By bear ing this principle in mind such tropical T i amphibians may usually be induced to breed in captivity. Bles in his excellent account of the life-history of Xenopus (1905) describes a method which will be found to be of general use. The pair of animals were kept in a Budgett tropical aquarium consisting of a glass bell-jar 20 inches in diameter dipping into a galvanized iron water-tank heated by a small Bunsen burner and oxygenated by plants of Vallisnemla. During summer the temperature of the water in the belljar was kept at about 25° C. The water was not changed. The frogs were fed daily with small earthworms or thin strips of raw calf’s liver until they would eat no more. In December the temperature was allowed to fall to 15°-16° during 1*‘1G-252--EI§ibI_'y0 of 1’hz/llmIwd'u~sja the day and as low as 5"-8° during the "”P"”f;::l”“l’8 "““‘°”°d °“t 1" night. As the temperature rose With the °;lﬁI1:ucca'1wity_M bmmpm_ onset of spring the frogs became more N’ mes, n1c.s'odcrnlsnigincnts. 4, actives Wilkmg “P out of the lethargic condition induced by the winter's cold. Breeding was induced by simulating the natural conditions of the rainy season. The temperature was raised to about 22° 0. Each morning and evening about two gallons of the water was drawn off, allowed to cool for twelve hours and then returned to the aquarium in the form of a fountain of spray from the upturned end of a glass siphon drawn out to a fine point so as to produce the effect of a shower of rain. Within a week or two breeding took place.

	The chief diﬁiculty in the way of cutting sections of _Frog’s eggs is due to the presence of the jelly-like envelope. This may be got rid of by prolonged soaking, six months or more, in -5% formalin (Ogushi, 1908), or by ﬁxing in Zenker’s ﬂuid and leaving the efgs 111 this ﬂuid renewing it after 2 to 3 days and continuing the treatment

	FIG. 253.-—Stages in the development of ]’l:.y/llunwdusa /1.3/po¢:h¢mal7"£alz's. E, eye; e.g, external gill; op,opercu1um; oz, otocyst.		FIG. 253.-—Stages in the development of ]’l:.y/llunwdusa /1.3/po¢:h¢mal7"£alz's. E, eye; e.g, external gill; op,opercu1um; oz, otocyst.

	~~for 8 to 14 days or longer, shaking gently so as to remove the envelopes (Kallius, 1908). '~~

	For cutting sections paraﬂin is commonly used but it should be supplemented by celloidin e.g. the clove-oil method mentioned under Ampimloxus.		For cutting sections paraﬂin is commonly used but it should be supplemented by celloidin e.g. the clove-oil method mentioned under Ampimloxus.
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	In the Urodeles the eggs are commonly laid singly in water and attached to water plants (Triton) or other solid objects such as logs or stones (Proteus, Necturus). In Oryptabranchus and Amphiuma they form a beaded string, adjacent envelopes being connected together by a narrow isthmus.		In the Urodeles the eggs are commonly laid singly in water and attached to water plants (Triton) or other solid objects such as logs or stones (Proteus, Necturus). In Oryptabranchus and Amphiuma they form a beaded string, adjacent envelopes being connected together by a narrow isthmus.

	Fertilization is rarely external (0'ryptob'ranchus——Smith, 1912). In the Newts the female takes up a spermatophore into the cloaca. ~~xx ' PRACTICAL HINTS-——AMPHIBIA 569~~		Fertilization is rarely external (0'ryptob'ranchus——Smith, 1912). In the Newts the female takes up a spermatophore into the cloaca.

	Such internal fertilization leads up to the condition in the Salamanders where fertilization takes place in the upper part of the oviduct and the developing embryo is retained for a less or more prolonged period within the body of the parent. In Salamcmdm mooculosa larvae about an inch in length are born in May resulting from fertilization during the preceding summer. '		Such internal fertilization leads up to the condition in the Salamanders where fertilization takes place in the upper part of the oviduct and the developing embryo is retained for a less or more prolonged period within the body of the parent. In Salamcmdm mooculosa larvae about an inch in length are born in May resulting from fertilization during the preceding summer. '

	As in the Anura wide differences exist in the richness of yolk and consequent size of the egg—the latter varying from under 2 mm. in the Newts to 6 mm. (Necturus) or 7 mm. in diameter (Org/ptobranchus japom'cus): so that here again though not to the same extent as in		As in the Anura wide differences exist in the richness of yolk and consequent size of the egg—the latter varying from under 2 mm. in the Newts to 6 mm. (Necturus) or 7 mm. in diameter (Org/ptobranchus japom'cus): so that here again though not to the same extent as in the Anura there is an excellent ﬁeld for investiga c tion into the inﬂuence of yolk upon developmental processes. The eggs of Urodeles are commonly collected under natural conditions and kept in earthenware dishes. Or the adults just about to breed may be brought into the laboratory and allowed to deposit their eggs in a suitable aquarium;


	~~F10~~. 254.-~~—Tadpo1e~~ of unknown Frog from Tropical Africa.
			Fig. 254. - Tadpo1e of unknown Frog from Tropical Africa.

	A, side view; B, ventral view. inc, huccal cavity; c.o, ('(‘.lllf‘.I\|l.r organ ; rz, anus; E, eye; e.g, external gill; u/,/', olfactory organ; up, operculum.		A, side view; B, ventral view. inc, huccal cavity; c.o, ('(‘.lllf‘.I\|l.r organ ; rz, anus; E, eye; e.g, external gill; u/,/', olfactory organ; up, operculum.

	the Anura there is an excellent ﬁeld for investiga c tion into the inﬂuence of yolk upon developmental processes. The eggs of Urodeles are commonly collected under natural conditions and kept in earthenware dishes. Or the adults just about to breed may be brought into the laboratory and allowed to deposit their eggs in a suitable aquarium;

	The Urodela form one of the relatively primitive groups of Vertebrates and their embryology‘ deserves much greater attention than it has hitherto received. Most of the older literature deals with special details i.n the development of the Newts but comprehensive monographs, including “normal plates” on the development of such genera as Proteus, Siren and Amphiuma are much wanted. A general account of the development of the American species of Uryptobranohus has been given by Smith (1912), while the Japanese species has been dealt with by Ishikawa (1918), De Bussy (1915) and Dan. de Lange, Jr. (1916). Of Necturus normal plates with accompanying tables have been worked out by Eycleshymer and Wilson (1910).		The Urodela form one of the relatively primitive groups of Vertebrates and their embryology‘ deserves much greater attention than it has hitherto received. Most of the older literature deals with special details i.n the development of the Newts but comprehensive monographs, including “normal plates” on the development of such genera as Proteus, Siren and Amphiuma are much wanted. A general account of the development of the American species of Uryptobranohus has been given by Smith (1912), while the Japanese species has been dealt with by Ishikawa (1918), De Bussy (1915) and Dan. de Lange, Jr. (1916). Of Necturus normal plates with accompanying tables have been worked out by Eycleshymer and Wilson (1910).


	The Gymnophiona—-—though an aberrant group of Amphibians highly specialized for a burrowing existence—are of much embryological interest and have provided the material for work of great morphological importance, such as that of Brauer upon the excretory organs. A general account of the development of Icltthyophis will be found in Sarasin (1887-90) and of Hypogeophis in Brauer (1897).		The Gymnophiona—-—though an aberrant group of Amphibians highly specialized for a burrowing existence—are of much embryological interest and have provided the material for work of great morphological importance, such as that of Brauer upon the excretory organs. A general account of the development of Icltthyophis will be found in Sarasin (1887-90) and of Hypogeophis in Brauer (1897).
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	Of the group in general it may be said that a comprehensive monograph on the development of each genus beyond Ichthyoplmls and Hypogeoph/is is a great desidcratum.		Of the group in general it may be said that a comprehensive monograph on the development of each genus beyond Ichthyoplmls and Hypogeoph/is is a great desidcratum.


	As standard ﬁxing agents for Amphibia corrosive sublimate and acetic acid, and for the later larval stages strong F lemming’s solution, may be used. For the early stages (segmentation and gastrulation) quite good results are obtainable from eggs that have been preserved alive in 10,°/O formalin: in this case it is well to treat the egg before dehydration for an hour or two with corrosive sublimate solution as without this precaution the formalin-preserved eggs are diﬂicult to stain well. When any other ﬁxing agent than formalin is used it is necessary, as a preliminary, to remove the egg envelopes. In the case of the larger eggs of the Urodela and Gymnophiona this can be accomplished with the aid of ﬁne scissors and forceps.		As standard ﬁxing agents for Amphibia corrosive sublimate and acetic acid, and for the later larval stages strong F lemming’s solution, may be used. For the early stages (segmentation and gastrulation) quite good results are obtainable from eggs that have been preserved alive in 10,°/O formalin: in this case it is well to treat the egg before dehydration for an hour or two with corrosive sublimate solution as without this precaution the formalin-preserved eggs are diﬂicult to stain well. When any other ﬁxing agent than formalin is used it is necessary, as a preliminary, to remove the egg envelopes. In the case of the larger eggs of the Urodela and Gymnophiona this can be accomplished with the aid of ﬁne scissors and forceps.

Z8600021: /* Appendix */

2018-06-16T00:01:39Z

Appendix

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Z8600021: /* Amphioxus */

2018-06-16T00:01:00Z

Amphioxus

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Z8600021: /* Amphioxus */

2018-06-15T23:55:24Z

Amphioxus

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2018-06-15T23:50:03Z

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