— 
“% & spout cemeh 
= 
— aU Ore 
x Sag 
at y 
7 = TOLL 
LL, il Ld, Yip 
Figs. 290-295. — pe hese Silos: Ceratodus. (After SEMON.) X 6. 290. 
Embryo at about the time of hatching. 291. Young larva. 292. Larva of two weeks. 
293. Larva of four weeks, ventral side. 294. Larva of six weeks. 295. Larva of ten 
weeks, 
A, Anus. AU. Auditory vesicle. 2G. External vi GS. Gill slits. A. Heart. 
M. Central nervous system. J/C. Mucous canals. O. Opercular flap. OZ. Olfac- 
_ tory organ. PF. Pectoral fin. PN. Pronephros. PS. Primitive segments. 5S. Mouth 
pit, stomodzeum. 
219 
