218 KANSAS UNIVERSITY SCIENCE BULLETIN. 



be doubted that the probability of the first spermatocyte being 

 witness of the reduction division is much increased when thus 

 interpreted by two independent observers. 



(e) The Accessory Chromosome. 



I have already, in another paper (19), taken up a compara- 

 tive study of the accessory chromosome in different insect sper- 

 matocytes, and shall not be obliged, for that reason, to enter 

 into a very lengthy discussion of the subject here. The great 

 interest attaching to this structure, however, compels me to 

 consider the work that has been done since the manuscript of 

 the earlier article was sent in for publication. This review will 

 concern, very largely, the investigations of Montgomery upon a 

 considerable number of Hemipteran species, which are set 

 forth in his paper under the pretentious title "A Study of the 

 Chromosomes in the Germ Cells of Metazoa." 



In his first work upon Euchistus, Montgomery describes a cell 

 element under the name "chromatin nucleolus" which corre- 

 sponded so closely to my accessory chromosome that I con- 

 cluded the two structures were identical. These similarities 

 were, the origin from a spermatogonial chromosome, the in- 

 tegrity and constancy of staining power and position during 

 the spermatocyte prophase, and participation in the division 

 act during metakinesis of a spermatocyte. 



Among the numerous changes of opinion recorded by Mont- 

 gomery in his latest work, there are several relating to his 

 "chromatin nucleolus" that materially alter the aspect of the 

 question. Perhaps the most important of these concerns the 

 origin of the element. I was some time in determining that 

 the accessory chromosome is a spermatogonial chromosome 

 which divides in the spermatogonia with the other chromatin 

 elements and comes over into the first spermatocyte as a formed 

 structure. The work of Sutton upon the early history of the 

 element in BracJiystola, however, was convincing in this respect 

 and confirmed me in the opinion I had already formed. I 

 therefore gave Montgomery the credit for this discovery, and 

 set it down as strong confirmation of the assumption that we 

 were dealing with similar structures in the two orders of insects. 



Upon this point Montgomery now completely reverses him- 

 self, and declares that his "chromatin nucleolus" is not a 

 spermatogonia! chromosome, but may be noted in the earlier 



