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THE AMEBIC AX NATURALIST [Vol.XLVI 



A further insight into the effect of the retention of 

 foreign chromatin is given by partially arrhenokaryotic 

 and partially thelykaryotic plutei. In such larvae, with 

 their asymmetrical bodies and skeletons, we may dis- 

 tinguish regional differences by nuclei of different sizes, 

 and by a study of segmenting eggs we may find how these 

 nuclei have arisen. In some instances we know that the 

 fertilization processes have been so modified that subse- 

 quent divisions of the egg contain only paternal nuclear 

 material and are paternal in character. In other regions 

 part or all of the foreign chromatin is present and has 

 modified development. 



The conditions noted in the plutei find correlation in 

 the following conditions in the egg. 



1. Betention of all chromosomes and dominance of one 

 species over another with respect to skeletal characters. 



2. Elimination of part of the chromatin and dominance 

 of one species over another with respect to skeletal char- 

 acters. 



3. Elimination of part of the chromatin and interme- 

 diate skeletal characters. 



4. Elimination of part of both paternal and maternal 

 chromatin and inhibition of development. 



The first three, at least, may all occur in a given lot of 

 eggs, and, since this is true, depend in part on chance,' 

 just as we may have imperfect mitotic figures in straight- 

 fertilized eggs. 



The second and third cases may indicate an incom- 

 patibility between the chromosomes and the cytoplasm 

 of the egg ; the fourth case, not this alone, but an incom- 

 patibility between the chromosomes themselves. 



Finally as to our ability to predict the character of the 

 adult from the characters of the larvse. 



It is clear that in Hipponoe and Toxopneustes we may 

 predict sex, since we have seen that maleness and a 

 heterochromosome of paternal origin are correlated. It 

 is thus evident that if chemically fertilized Hipponoe and 

 Toxopneustes eggs develop to sexual maturity these in- 



