File:Keibel1910 fig25-27.jpg

Note - Magnifications refer to original print versions.

Fig. 25. (X 5.)

Side view of embryo 23 days 10 hrs. old, length 9 mm, 20 — 22 pairs of myotomes. General outline of the body straighter. Head free from yolk. Caudal enlargement becoming free. Optic vesicles and forebrain much larger. Mandibular, hyoid, first branchial, and common anläge of second and third branchial arches well defined. Otic vesicle visible above hyoid arch.

Fig. 26. (X 5.)

Side view of embryo 24 days 22 hrs. old, length 10 mm, 23 — 24 pairs of myotomes. General outline of body of embryo straighter, less curved laterally. Head and caudal extremities free from yolk. Yolk becoming oval. Optic vesicles prominent. Ear better defined. Olfactory pits present. The mandibular, liyoid and first branchial arches are distinct. The second and third branchial arches are not yet differentiated, a slight process on the first branchial indicates the beginning of the gill bar. The anläge of the heart is visible just beneath the arches.

Fig. 27. (X 5.)

Side view of embryo 26 days old , length 1 1 mm , 26—27 myotomes. General outline of body straighter than in preceding stage. Head projects some 3 mm beyond margin of yolk; tail projects 1.2 mm, is thinner laterally but broader dorso-ventrally. Eye, ear, nasal pits and mouth well defined. Maxillary process discernible. Mandibular arches longer, but ventral ends widely separated. Second and third branchial arches formed. Gill bars present on three branchial arches. Anterior limb buds indicated; faint anläge of posterior limb buds. Yolk pear-shaped. Heart prominent. First surface capillaries present although not indicated in figure.