m'clung: spermatocyte divisions of the locustid.k. 191 



those favorably situated the quadripartite nature of the future 

 chromosomes manifests itself very distinctly. 



This important stage in the history of the first spermatocyte 

 chromosomes first received attention at the hands of Paulmier 

 in his studies upon Anasa. Almost at the same time I found 

 structures in the Orthopteran spermatocytes so nearly identical 

 that it would be impossible to distinguish any marked differ- 

 ence between them. The Locustid material, equally with the 

 Acridian, permits an exact determination of the chromosome 

 structures, which later become so masked as to be indeter- 

 minate. 



The interest attaching to the construction of the spermato- 

 cyte chromosomes is so great as to warrant an account of the 

 process, although, in general, it is largely a repetition of what 

 has been given for Anasa and Hippiscus. As early as the stage 

 represented in figure 6, it becomes noticeable that the chroma- 

 tids near the middle of the thread tend to diverge from each 

 other, leaving a diamond-shaped space. This becomes more 

 pronounced, and it is soon seen that each half of the thread is 

 broken across at the same level, resulting in the production 

 of a chromosome of four parts. Still retaining their general 

 shape, these segments shorten and broaden until they are al- 

 most the size of the metaphase chromosome. 



All variations conceivable upon the wider separation of the 

 halves along the longitudinal split, the movement of the parts 

 upon the line of separation at right angles to the original cleft r 

 or of approximation and rotation of the free segmented ends 

 are found. Thus do we get the cross-shaped, the double-V, the 

 figure-of-S, the Y-shaped and ring figures, in figure 11. Many 

 of the rings give the impression, upon superficial examination,, 

 of loops with their free ends crossed. A careful examination 

 will always reveal the fact, however, that what appears to be 

 the crossed ends is really the middle portion of the segment, 

 with the chromatids drawn out along the plane of the cross- 

 division. In segments that are favorably placed, there is never 

 any difficulty in correlating the structures with the typical one 

 of a cross-split lengthwise of each arm. 



The quadripartite nature of the chromatin segments may be- 

 determined, as already indicated, almost as soon as the longi- 

 tudinal split occurs. From this time on until the chromosomes- 



