IC)| EVIS HOWARD BEKRV. 



somes at the time of synapsis. The mode of division of this 

 bivalent accessory was not positively determined, but he suggested 

 that the similarity in its formation gives some evidence that it 

 may behave in the same way as the other chromosomes in both 

 mitoses, dividing first reductionally and then equationally, thus 

 being equally distributed to all of the spermatids. Nearly at the 

 same time Wallace ('05) published her final paper on the sperma- 

 togenesis of Agalcna, a spider, with results quite different from 

 those of Montgomery on Lycosa. I will quote her brief sum- 

 mary, p. 182. 



" i. The spermatogonia contain two accessory chromosomes 

 and thirty-eight other chromosomes. 



" 2. In the primary spermatocytic division, the two accessory 

 chromosomes pass over undivided into one of the daughter cells. 

 The reduced number of other chromosomes is nineteen and these 

 divide transversely. 



" 3. In the secondary spermatocytic division, the two accessory 

 chromosomes again pass over undivided into one of the daughter 

 cells. The nineteen other chromosomes divide longitudinally. 



"4. Only one fourth of the spermatozoa contain the accessory 

 chromosomes. 



" 5. Apparently the remaining three fourths of the spermatozoa 

 degenerate after almost or altogether reaching maturity. In this 

 respect they are regarded as homologous to the polar bodies 

 thrown off by the ovum." 



In view of these perplexing and contradictory accounts, I under- 

 took the present work on Epcira sclopetaria to see if I could throw 

 any light on the question. Owing to lack of material I have 

 been able to study only one family, the Epeiridae. The results 

 which I have to offer on the origin and behavior of the accessory 

 chromosome here are consistent with those of McClung, Sutton 

 and Wilson, already mentioned, and also with those of Blackmail 

 on the myriapods ('03), but they give no explanation of the re- 

 results of Wallace and Montgomery, which are widely different 

 from my own. At a future time I hope to examine other families 

 of spiders with respect to this discrepancy ; certainly in none of 

 my preparations of Epcira do I find any trace of degenerating 

 spermatozoa. 



