658 



6ASHF0RD DEAN, 



continuing their growth, they bend downward, tailward of the rectum 

 and establish their outer opening. Very similar conditions have been 

 described and figured in the Teleosts. 



c) L i V e r , y o 1 k. 

 The liver takes its origin in the stage of PI. 9, Fig. 4, as a 

 broad upwardly directed fold of the dorsal wall of the gut. In the 

 stage of PL 9, Figs. 6, 7 ?, it appears in surface view as a whitish 

 mass lying on the dorsal wall of the yolk sac immediately at the left 

 side of the trunk. It is now pocket-like, its blind end directed some- 

 what outward and forward, its hinder portion somewhat flattened, 

 and communicating with the cavity of the gut through a narrow slit- 

 shaped opening. These conditions are in part illustrated in Figs. H, 



Figs. H — K. Transverse sections of Amia 

 shortly before hatching. Fig. H through gut aud 

 hindmost portion of liver. Fig. J through gut 

 and middle region of liver. Fig. K through gut 

 and anterior tip of liver. BC Body cavity, G 

 gut, L liver, Y yolk. 



J, K, transverse sections through the region of the yolk sac of an 

 erabryo shortly before hatching; thus in Fig. H, the hindmost section, 

 the Position of the liver is showu at L: auteriorly the liver becomes 

 a well marked diverticulum of the wall of the gut; in Fig. J the 

 lumen of the liver, L, is separate from that of the gut, (r, although 

 it still is continuous ventrally with the yolk, Y; in the foremost 

 section, Fig. K, passing through the anterior tip of the liver, the gut 

 has become flattened dorso-veutrally, is broadly fused with the dorsal 

 wall of the body cavity, and is separate, below from the yolk, and 

 at the side from the liver. The subsequent growth of the liver is as 

 foUows: its coical condition becomes ramose, and the organ enlarges 

 greatly in size, fitting itself into the space at the side of the visceral 

 cavity, and between the stomach and intestine. In a transversa 



