M CLUNG : SPERMATOCYTE DIVISIONS OF THE ACRIDID^. 79 



Xiphidium, there is as yet no noticeable appearance of the accessory 

 chromosome so strikingly visible in the spermatogonia of the Locus- 

 tidcP. 



Immediately following the assembly of the spermatogonia! chromo- 

 somes at the poles of the mother cell, they commence to disintegrate 

 in preparation for the formation of the nnclear thread of the sperma- 

 tocyte. This is a very interesting process, and was carefully observed 

 in a follicle where the relative position of the cells clearly indicated 

 the phases of development. 



The first thing to be noted is the change in the character of the 

 chromosomes. Heretofore smooth in outline and homogeneous in 

 structure, they now become irregular in form and of a granular nature- 

 A little later it will be seen that the dispersion of the chromatic mate- 

 rial has progressed so far that almost all trace of the individual chro- 

 mosome has disappeared. Only here and there does a slight massing 

 of the chromomeres indicated the position of a former chromosome. 

 (Fig. 4.) 



Such, however, is not the fate of all the chromatic elements. One, 

 refusing to give up its identity, maintains its form among the re- 

 mains of its fellows and passes into the spermatocytes unchanged, to 

 become the accessory chromosome, whose future history will be con- 

 sidered later. 



From the scattered mass of chromatin granules produced by the 

 breaking down of the spermatogonia! chromosomes, there is now con- 

 structed a thin, granular thread which marks a very early stage of 

 spermatocyte prophase. This becomes more definite in outline and 

 thicker in structure until a single, much-convoluted thread is formed. 

 (Figs. 5, 6, 7.) While it is a difficult matter to determine with cer- 

 tainty whether or not the end of this process results in the formation 

 of a single thread, I am inclined to believe that it does. 



But however this may be. there is no doubt that shortly afterwards 

 a series of cross-divisions results in the establishment of a number of 

 long, irregular chromatin rods. The number of these is either the 

 same, or very nearly the same, as that of the chomosomes appearing 

 in the spermatocytes. Figs. 8 and 9 show the conditions prevailing 

 at this time. Shortly after this a marked change takes place in 

 these chromatin segments. The coarsely granular character thus far 

 noticeable gives way to a much finer granulation which accompa- 

 nies a shortening and loosening of the chromatic segments. The chro- 

 matin here gradually passes into thread-like processes whicli extend 

 throughout the nucleus and join the rods and loops together. The 

 form and structure of these elements is subject to considerable varia- 

 tion, as may be observed from an examination of Figs. 10, 11, Vl, and 



