No. 549] A CASE OF POLYMORPHISM 547 



I m • i 1 1 u' unable to feed and 1 1 in- continue their development, 

 are obliged to remain at approximately the same diver- 

 gent sizes at which they are born. 



In regard to the resting eggs, they are, of course, as are 

 the males, produced by all three types, and but rarely by 

 the smaller saccate form. The number produced by one 

 individual varies greatly with the degree of nutrition. 

 But one to three are matured if the females are poorly 

 fed after fertilization; whereas as many as six are fre- 

 quently present at one time in the body when nutrition is 

 high, and very rarely as many as nine may be seen. The 

 large campanulates usually show a high number, but it 

 does not exceed the maximum produced by the humped 

 form. The color of the egg, which Rousselet uses as a 

 specific character, is variable in this species. In in- 

 dividuals fed on Paramecia the eggs are quite white; 

 in individuals reared on Brachionus they are light yellow 

 to orange; while in Moina-ieedeva they are dirty white 

 to brown. Again, the volume of yolk, i. e., the filling oi 

 not tilling of the egg cavity, which Rousselet also regards 

 as important, I find to be highly variable in the eggs 

 of both this species and of A. brightweUi. It is par- 

 tially a matter of the age of the egg: but eggs are fre- 

 quently deposited in the most different conditions with 

 regard to this character. There remains the size of the 

 egg and the appearance of the egg coats, both of which are 

 highly characteristic and relatively uniform. The size 

 of the egg is much less, relative to the size of the animal, 

 than is the case in A. brightweUi; but the actual size is 

 larger and exceeds the dimensions given by Rousselet 



indefinite amount of material, grown under very diverge 

 conditions, are the most uniform and at the same time the 



