CHROMOSOMES OF ANASA TRISTIS. 351 



Paulmier and of Montgomery seemed to be cleared up and the 

 phenomena in this order brought into agreement with those 

 of the other insects. To this was added the confirmatory 

 work of Stevens upon several orders of insects, the study 

 of Lefevre and McGill on Anasa, and more recently that of 

 Morgan on aphids and phylloxerans. Directly opposed to all 

 this are the observations of Foot and Strobell upon A7iasa 

 tristis, the form studied in detail by Paulmier, Montgomery 

 and Wilson. Their contention, in brief, is that the number 

 of spermatogonial chromosomes is even instead of odd, that 

 there is no dimorphism of the spermatozoa due to the presence 

 in one-half their number of the accessory chromosome, and 

 that there is no evidence to show that the theory of chromo- 

 some individuality receives any support from observed mor- 

 phological continuity of any of the chromosomes. Aside from 

 these major questions there are others, such as the history 

 and fate of the plasmasome, upon which these authors are in 

 disagreement with other investigators. 



The issues here defined are so clear-cut and definite and 

 their settlement of so much importance that the senior author 

 of the present paper was led to offer his services for a reex- 

 amination of the whole question. This offer met a hearty 

 response from Professor Wilson, who sent not only live mate- 

 rial, but his entire series of mounted slides, including those 

 used by Paulmier. Professor Lefevre has been kind enough, 

 also, to permit the use of his slides. Miss Strobell, writing 

 for Miss Foot, expressed a lively interest in the proposed set- 

 tlement of this problem, but was unable to send the prepara- 

 tions used in their studies, because these had all been de- 

 stroyed on account of limited storage room. It is to be 

 regretted that this material is not available for comparison, 

 since it is upon it that the only divergent observations have 

 been made; but since specimens from the same locality, pre- 

 pared by all methods, including the special ones employed 

 by the Misses Foot and Strobell, are at hand, there can be no 

 reasonable doubt that it is representative. 



To reduce the possibility of the influence of preconception 

 to the lowest possible degree, the junior author has worked 

 through the entire problem without knowledge of the work 

 done by others, and without promptings from the senior 

 author except such as were given by a series of questions for 



