50 
MONICA TAYLOR. 
Fig. 14. — ’Ventral view of larva of Stage 33. o. o. Opercular opening. 
Fig. 15. — A larva of Stage 33. o. o. Opercular opening. 
Fig 16. — Stage 35. 
PLATE 3. 
Fig. 17. — Paraffin sagittal section tlirougli an egg, Stage 8. s. Space 
underlying blastoderm, y. s. Yolk syncytium. 
Fig. 18. — A celloidin sagittal section, 25 fx. thick, through an egg of 
Stage 10. ec. Ectoderm, en. Endoderm. n.p. Neural plate, y.s. 
Yolk syncytium, y. s. n. Yolk syncytium nuclei. 
Fig. 19. — Transverse section through a larva of Stage 32. The 
operculum has grown backwards to the point of origin of the pectoral 
fins. a. c. V. Anterior cardinal vein. d. a. Dorsal aorta, i. j. Inferior 
jugular, o. Operculum, s. a. Subclavian artery, s. g. Shoulder girdle. 
s. V. Subclavian vein. 
Fig. 20. — A horizontal section through a larva of Stage 25. cce. 
Ccelom. g. c. Gill-chamber. 1. Liver, m. Mesencephalon, p-/- Pectoral 
fin. o. Operculum. I, II, III, IV. Branchial arches 1-4. 
Fig. 21. — A transverse section through a larva of Stage 26. a. c. Ali- 
mentary canal, a. d. Archinephric duct. b. d. Bile-duct. cce. Ccelom. 
d. a. Dorsal aorta, d. p. Dorsal pancreas. Z. Liver, s. Spleen, y. Yolk. 
Fig. 22. — Sagittal section through a larva of Stage 34. The figure 
showing the brain is drawn from one section, that showing the lower 
jaw from another section, the distance between the two sections being 
20 y. a. 0 . Olfactory organ, c. Cerebellum, c. pi. Choroid plexus, 
c. g. Gill-cavity, h. g. Habenular ganglion. I. Infundibulum, ol. 1. 
Olfactory lobes, o. 1. Optic lobe. thy. Thyroid, t. Tongue, v. t. 
Velum transversum. II. Optic nerve. 
PLATE 4. 
Fig. 23. — Transverse section through a larva of Stage 29. a. c. v. 
Anterior cardinal vein. IV. ef. bra. Fourth efferent branchial. Ill, 
IV, g. a. Third and fourth branchial arch. g. c. Gill cavity, p. 
Pericardium, p. o. Pore-like opening into gill-chamber, y. s. Yolk-sac. 
Fig. 24. — Transverse section through a larva of Stage 35. d. a. Dorsal 
aorta, gr. 5. Gall-bladder, i. 7*. v. Inter-renal vein. Z. Liver. p>ZZ. Pseudo- 
lymphatic tissue surrounding kidney, jp.-y. Pyloric valve, p.a. Pancreas, 
s. Stomach (pylorus), s.i.v. Hepatic vein. 
Fig. 25. — Sagittal section through an embryo of Stage 24. a. c. Ali- 
mentary canal, d. a. Dorsal aorta, n. Notochord, s. c. Spinal cord. 
