THE DEVELOPMENT OF SYMBRANCHUS MARMORATUS. 51 
s.i.v. Sub-intestinal vein. y.s. Yolk syncytium, y.s.n. Yolk-syncytium 
nucleus. 
Fig. 26. — Sagittal section through a larva of Stage 32. a. Atrium. 
h. Bulbus. a. c. Alimentary canal, s.v. Sinus venosus. v. Ventricle. 
V. V. Vitelline vein = sub-intestinal vein = portal vein. y. s. Yolk- 
syncytium. 
Fig. 27. — Transverse section through a larva of Stage 33. a. c. Ali- 
mentary canal, d. a. Dorsal aorta, g. Glomerulus, g. a. Glomerular 
artery, i.r.v. Interrenal vein. ia. Intersegmental artery. 7c. t. Kidney 
tubules. 1. Liver, n. Notochord, y. Yolk. 
Fig. 28. — Brain dissected from a larva of Stage 34. a. Dorsal ; 
B. Ventral view. c. Cerebellum. 1. I, Lateral lobes of infundibulum, 
m. 0 . Medulla oblongata, o. 1. Olfactory lobes, t. Telencephalon, th. Tha- 
lamencephalon. t. o. Tectum opticum. 
