No. 446.] 



DESMOGNATHUS FUSCA. 



ventral to heart and liver and a smaller one ventral to the anus. 

 The entire yolk mass, which is wholly cellular, is enclosed within 

 the peritoneum and is morphologically the equivalent of the mid- 

 dle portion of the intestinal tract in which a lumen has not as yet 

 appeared. Fig. 5 shows four cross-sections of an embryo a little 

 older than that of Fig. 4 and taken from a single series, the 

 first through the liver, the second through the yolk at its great- 

 est circumference, the third through the hip-girdle and rectum 

 and the fourth through the cloaca, with the hind-limbs at the 

 side. The numbers attached to each are those of the sections 

 as numbered m the series. These show the same relationships 

 as seen in Fig. 4, the second especially, in which two lateral 



coelomic spaces may be seen dorsal to the yolk-mass, separated 

 by a mesentery. In the first the alimentary canal {esophagus 

 or beginning of stomach) is suspended between dorsal and ven- 

 tral mesenteries, in the latter of which lies the already well- 

 developed liver, while in the former is seen the beginning of a 

 pancreas. In the third section are seen the two lateral cck- 

 lomic cavities, dorsal and ventral mesenteries, the hip girdles and 

 the heads of the femora, and in the fourth are the last (most 

 posterior) remnants of the coeloms, the open cloaca, and the two 

 legs, the one cut through the femur, and the other through tibia 

 and fibula. 



Smith College, 

 Nov., 1903. 



