M 'CLUNG : SPERMATOCYTE DIVISIONS OP THE LOCUSTID.l'. . 203 



for in some species it is possible to distinguish a particular 

 chromosome in all the spermatocytes. This is strikingly the 

 case in Anabrus, where there is always one chromosome very 

 much larger than any of the others. It exceeds in size even 

 the accessory chromosome, and might be mistaken for it were 

 it not for the difference in form. It is, however, typically a 

 tetrad, and shows the four chromatids, while the accessory 

 chromosome exhibits the usual spermatogonial condition. 



As was indicated under the head of "Observations," the pro- 

 phase tetrad characteristic of Anasa and Hippiscus is again ex- 

 emplified in the Locustid cells. So close is the resemblance of 

 the maturation chromosomes of these various insect cells in 

 their early stages, that I now regard it as practically established 

 that they are commonly present in all insect spermatocytes. 

 No more important evidence regarding chromosome structure 

 and behavior can be obtained than that afforded by these ele- 

 ments. Particularly are the ring figures of value in the deter- 

 mination of the sequence of the longitudinal and cross divisions, 

 and upon this point the material from the two families is 

 equally convincing and positive in demonstrating that the first 

 spermatocyte mitosis witnesses a separation along the longitu- 

 dinal cleft of the spireme thread. 



I should like to emphasize the fact that the chromosomes in 

 both the Orthopteran families studied have been carefully 

 traced from their earlier appearance down to the time of their 

 dissolution in the spermatid through such a gradual series of 

 changes that there can be no reasonable doubt of the accuracy 

 of the conclusion set forth in these papers. The Orthopteran 

 material possesses one distinct advantage over the Hemipteran, 

 in that the point of cross-division is always marked by the same 

 sort of a protuberance as is to be distinguished in the early 

 chromatin segments. When the two free ends of the element 

 are brought around to form a closed ring, the last particle of 

 doubt regarding the position of the planes of separation marked 

 out for the two spermatocyte divisions is dispelled. 



This diagnostic character seems to be lacking in the chromo- 

 somes of the Hemiptera, and Paulmier, in his work on Anasa, 

 depends for his criteria of orientation upon the relative lengths 

 of the chromosome axes. Such a feature would be valueless in 

 Orthopteran cells, because, as has been shown, the chromatids 



