BLATTELLA GERMANICA. 9 



of the division of the tetrad. In this form there can be no doubt that 

 reduction occurs in the first spermatocyte division. The element x is 

 very often concealed by the polar aggregation of chromatin, but it is 

 sometimes as conspicuous as in figures 131 and 132. The spermato- 

 cytes of the second order go into a complete resting stage before they 

 are completely separated, and one of a pair shows the element x, while 

 it is lacking in the other (fig. 133). At the close of the resting stage 

 the chromosomes appear as 11 pairs of rods of considerable length, 

 which gradually shorten and thicken and usually bend at the center, 

 forming U's or V's (figs. 134-138). In one stage these double U's 

 look much like tetrads (fig. 138). The rods straighten again as they 

 shorten still more (fig. 139), become more closely approximated, and 

 finally form dumbbells, as in figure 141. 



The element x is, of course, present in only one-half of these 

 nuclei. In the equatorial plate, figure 142, it is absent ; in figure 143 

 it is present, but can not be distinguished from the other chromosomes, 

 while in figure 144 it is rendered conspicuous by its spherical form 

 and isolated position. In only a few cases has it been possible to dis- 

 tinguish X in the spindle. Figures 146 and 147 show two of these 

 cases where this element is clearly double and of different form from 

 the other chromosomes. It is probable that it divides and so goes 

 into one-half of all of the spermatids, as in McClung's typical cases 

 of the accessory chromosome. Figure 145 shows the usual appear- 

 ance of the other chromosomes in metaphase. The two spermatids of 

 a pair are always alike so far as any evidence of the presence of the 

 element x is concerned (fig. 148). Figure 149 is an exceptional case, 

 where one chromatin element (possibly x) has evidently divided late 

 and been left out in the cytoplasm ; a smaller chromatin granule 

 is also present in the cytoplasm of each spermatid. All of the sper- 

 matids, as in Stenopehnatiis , develop a deeply-staining body, which, 

 however, in this case is usually centrally located and often appears 

 double (figs. 150-152). 



The spindle-remains {Spindelreste) forms a very conspicuous body at 

 one side of the nucleus in the spermatids, and occasionally a mass of 

 chromatin, probably due to imperfect mitosis, is found near the spindle- 

 substance (fig. 150). The mass of spindle-substance at first appears 

 structureless, but soon assumes the condition shown in figures 150 to 

 152. In one individual many of the spermatids had two balls of spindle- 

 material (fig. 152), and the resulting later stages were double-tailed 

 (fig. 153). Figure 156 shows how the spindle-substance goes into the 

 tail and gradually disappears as the tail lengthens. 



