576 



CHARLES R. STOCKARD 



chromatophores do not, however, assume any arrangement 

 with reference to the islands of cells and as mentioned above 

 they retain their original condition as separate cells instead of 

 fusing into syncytial masses, as is the case in specimens with a 

 free blood circulation. 



Fig. 35 The arrangement of red blood corpuscles in more or less connected 

 endothelial sacs on the ventro-lateral surface of the yolk in an embryo 14 days 

 old that had never had a circulation of fluid in its vessels. All of these blood 

 cells wandered away from the caudal body regions of the embryo during early 

 stages. The chromatophores are irregularly scattered among the old blood- 

 islands. Od, oil drop. 



Figure 35 illustrates a group of blood masses on the yolk-sac 

 of an embryo 14 days old. In this specimen there had been 

 absolutely no circulation or movement of the blood fluids within 

 the vessels at any time. This is most important to know in the 

 case of all specimens without a circulation at the period they 

 chance to be examined. I shall return to this point below. The 

 cell groups in the specimen without a circulation are arranged 

 somewhat like a vascular net in the region illustrated by figure 35, 

 yet they present a deadly still appearance as contrasted with 

 the lively movement of the corpuscles within the yolk vessels 

 of a normal individual. The erythrocytes forming these islands 



