410 EDITH PINNEY 



Menidia fertilized by the sperm of Ctenolabrus (15) with the 

 figures given by Herbst (7) for Sphaerechinus 9 X Strongylo- 

 centrotus cT, by Baltzer (1) for the eggs of Strongylocentrotus, 

 Echinus, and Arbacia fertihzed by Sphaerechinus sperm, and 

 bj^ Tennent (16) for the reciprocal crosses between Arbacia and 

 Toxopneustes. 



The behavior of the chromatin in the cross between Echinus 

 acutus 9 X Echinus esculentus cf, reported by Doncaster and 

 Gray (4), shows shght differences from those described by the 

 foregoing investigators. In the latter cross the chromosomes 

 form vesicles and are eliminated during the anaphase. The 

 vesicles make their appearance in the prophase, which may in- 

 dicate that the origin is different from that causing the lagging 

 occurring in other forms. It appears that lagging was also 

 observed by these authors in connection with the cross Echi- 

 nus acutus 9 X Echinus milearis cf, for of this cross they say, 

 "In the hybrid eggs we found that some of the chromosomes 

 developed vesicles, but no other elimination occurred except 

 the possible non-division of certain chromosomes, about which 

 we are uncertain." 



Godlewski (5) reports chromatin elimination in his interclass 

 cross between Echinus 9 and Antedon cf. The Antedon 

 chromosomes take part in the first mitosis, but are eliminated 

 later. Counts of polar views of anaphase groups are given as 

 evidence. The figures accompanying this paper are unsatis- 

 factory in that they give no evidence as to the manner in which 

 eUmination is accomphshed. 



In the cross studied by Kupelwieser (8) we have an extreme 

 case of elimination, due probably to factors operating earlier 

 in development. 



The actual ehmination of chromosomes from the mitotic 

 mechanism rests on more conclusive evidence in the case of 

 echinoderms than it does in that of fishes. 



Unequal distribution of paternal chromatin unquestionably 

 occurs in both, although aside from its casual mention by Don- 

 caster and Gray (4), Herbst (7) is the only investigator to report 

 this for echinoderms. Baltzer's figures, however, show unmis- 



