PLATE 21 



EXPLAXATIOX OF FIGURES 



84 A living ten-day Fundulus embryo in which the heart anlage was de- 

 stroyed at the 60-hour stage. Erythrocj-tes developed anterior to the pectoral 

 fins, on the anterior yolk just ventral to the pericardium, and in a peculiar posi- 

 tion dorsal to the posterior .yolk, as well as in the intermediate cell mass and on 

 the posterior yolk. 



85 A living twelve-day Fundulus embryo in which the heart anlage was 

 destroyed at the 60-hour stage. At the same time the head was severed. A large 

 'pericardial' cavity has formed. Erythrocytes formed between the otocysts, in 

 the ducts of Cuvier, and in the intermediate cell mass. 



172 



