190 KANSAS UNIVERSITY SCIENCE BULLETIN. 



if anything, tend to confirm the view that there is a possibility 

 of complete rearrangement of the chromomeres in the different 

 chromosomes. Concerning this, however, the accessory chro- 

 mosome is much more conclusive and convincing, as will be 

 shown later. 



Disregarding the relations of the chromosomes of the two 

 generations, it is evident that from the material of the sperma- 

 togonial elements there is formed the thread of the spermato- 

 cyte prophase. As indicated in figures 3 and 4, this is at first 

 composed of a single series of chromomeres. But in a slightly 

 later stage, represented by figure 5, it becomes plain that the 

 thread is wider and at the same time double. A careful inves- 

 tigation will show that the halves of the thread are exact dupli- 

 cates of each other, each granule of the one having its mate in 

 the other. There is but one conclusion to be derived from the 

 appearances just described, which is that the double thread is 

 formed by a longitudinal division, granule by granule, of the 

 original filament. The evidence afforded, not only by the 

 Locustids, but by all the Orthoptera, is unequivocal on this 

 point. The cleavage of the thread is not exaggerated in the 

 accompanying figures, and is distinctly in evidence even under 

 ordinary conditions of illumination and magnification. 



Much controversy has recently arisen among both botanists 

 and zoologists concerning an appearance of the chromatin in 

 the prophase, which has received the common designation 

 "synapsis," by which is meant, usually, a one-sided contrac- 

 tion of the chromatin in the nuclear vesicle. No such stage in 

 the nucleus could be found in Hippiscus, and it is likewise ab- 

 sent in the Locustid cells. I therefore repeat the assertion 

 made in the previous paper (17), that in properly fixed mate- 

 rial derived from Orthopteran sources the first spermatocyte 

 prophase shows no unilateral massing of the chromatin. 



Shortly after the formation of the double spireme, it is to be 

 seen that the thread is no longer — even if it was previously — 

 continuous, but is composed of segments (figs. 5-10) , So early 

 as this it is possible to observe that the segments are of very 

 unequal lengths. The extent of this inequality may be gath- 

 ered by consulting figures 6 and 7. Even in this early stage 

 the real structure of the segments may be determined, and in 



