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HUBERT DANA GOODALE 



found in which cleavage from the start proceeded with consider- 

 able regularity in the lower hemisphere. Still other eggs are 

 intermediate in their behavior. Thus the eggs of Spelerpes 

 exhibit many of the amphibian types of cleavage. 



Irregular cleavages. Fig. 6 shows an extreme case in which 

 the first furrow formed a small circle on the upper hemisphere 

 of the egg which nevertheless produced a normal embryo. Hert- 

 wig ('93) has described similar cases. Fig. 5 represents an inter- 



a 



Figs. 3 and 4 



mediate type. All gradations to perfectly equal division may be 

 found. Something like 30 per cent of all eggs show marked 

 deviation from equality. On the other hand, cases in which the 

 second plane divided the egg unequally are very rare, one of which 

 is shown in fig. 8. 



Konopacka ('08), in centrifuged eggs, observed that the nucleus 

 in eggs showing unequal first cleavages was displaced laterally. 

 Doubtless this has happened in these eggs. In the egg shown in 

 fig. 7, the formation of the second furrow was seen. Fig. 7a 



