466 



BERTRAM G. SMITH 



I 3 



73 



74 



75 



I 3 



2' ' 2 



2 2 



3 I 



78 



79 80 81 



Figs. 73 to 81 Fourth cleavage of Cryptobranchus allegheniensis, X 4t. All 

 the figures are of the upper hemisphere. Figure 73 and 74 are drawn from the 

 living egg; the others are camera drawings from preserved material. Figures 

 73 and 74 represent early stages of fourth cleavage; figurp 80 is from the same egg 

 shown in figure 74, representing the condition three hours later. Figure 81 is 

 drawn from the egg photographed for figure 209. 



(b) From, the third cleavage furrows the remaining four 

 parts of the fourth cleavage furrows may continue latitudinallj'', 

 forming a complete circle or oval enclosing eight micromeres 

 (fig. 81) ; or one or more of these four parts may continue approx- 



