ORTHOPTERAN SPERMATOGENESIS 719 



1. Hippiscus type. The striking variation of form appearing 

 among the metaphase chromosomes of the first spermatocyte 

 gives way in the second spermatocyte to as marked a uniformity. 

 The paired, straight rods of the first spermatocyte anaphase 

 reappear in the succeeding metaphase in the same sizes and forms, 

 and between these two stages — ^through the telophase and pro- 

 phase — they may often be recognized individually. This visible 

 continuity is a variable matter in different species, but almost 

 always the individual elements may be traced without confusion. 

 Here, as elsewhere, the accessory chromosome comes into prom- 

 inence during the prophase by reason of its greater density, 

 clearly indicating the cells wherein it lies. To some extent, 

 however, it shows a loosened structure like the euchromosomes 

 and again in this way presents a parallelism with them. The 

 changes between the two generations of spermatocytes take place 

 rapidly, and occasionally cysts are formed in which appear telo- 

 phases of the first spermatocyte and metaphases of the second 

 spermatocyte. It is evident that no profound changes are ac- 

 complished at this time — everything points to a rapid rearrange- 

 ment of formed chromosomes into a new division figure with the 

 least possible change or movement of the cell elements. 



A study of the metaphase figure discloses physical conditions 

 very similar to those of the spermatogonia. The chromosomes 

 are straight rods arranged radially, for the most part, about the 

 spindle axis with fiber attachment at the inner ends (figs. 16 to 19, 

 3 1 , 49 to 58) . The same series of sizes apparent in the earlier gener- 

 ation again presents itself, but now in a single instead of a dupli- 

 cate grouping. Presence or absence of the accessory chromo- 

 some marks the two classes of cells descended from each second- 

 ary spermatogonium. One notable difference between the chro- 

 mosomes of the spermatogonia and of the second spermatocytes 

 manifests itself. During the earlier period the chromosomes 

 were much extended and the chromatids were closely apposed, 

 while in the second spermatocyte the chromosomes are shorter 

 and show a marked divergence of their halves. This tendency 

 of the chromatids to separate may go to the extreme of extension 

 in a straight line if the chromosome happens to lie toward the 



