FERTILIZATION AND CLEAVAGE 

 TABLE 5 



TIME OF FIRST CLEAVAGE OF SOME SPECIES, IN MINUTES AFTER FERTILIZATION 



99 



It will be seen that the eggs of some species cleave more rapidly than 

 those of Arbacia punctulata, some less rapidly. There seems to be no 

 relation between the size of the egg and the rate of cleavage. One 

 might think that the cleavage rate of a small egg would be faster than 

 that of a large egg. But the small egg of Tripneustes esculentus, 84 (j, dia- 

 meter, cleaves more slowly (90 min. at 22 °C.) than the large egg of 

 Dendraster excentricus, 1 14 [x diameter which cleaves in 47 min. at 22 °C. 

 It may be noted that large eggs may come from small species, (e.g.^ 



