BILATERALITY IN CRYPTOBRANCHUS 



381 



greater stability. We shall here consider the relation of the 

 excentric internal structure of the early blastula to some other 

 features of organization. 



Figs. 20 to 25 Meridional sections taken in the median plane of bilateral 

 symmetry of eggs of Cryptobranchus allegheniensis in early to late blastula 

 stages. *S, segmentation cavity or blastocoele. Fig. 20, stage6; fig. 21, stage?; 

 figs. 22 and 23, stage 8; figs. 24 and 25, stage 9. The figures were drawn with the 

 aid of a camera lucida. X 8. 



