spermatogenesis CO I 



instead of one, in the first spermatocyte equatorial plate (Fig. 285) 

 and also in the second spermatocyte plates (Figs. 288 and 289). 

 The chromatin in the spermatid nucleus does not stain so deeply, 

 and here it can be demonstrated that there is a chromatin nucleus in 

 all of the spermatids (Figs. 292 and 293), and the odd chromosome 

 besides in half of them (Fig. 292). Here also the female somatic 

 chromosome number is 28. Fig. 294 shows some of the chromo- 

 somes overlapping each other, but they are really entirely separate 

 from one another, lying at slightly different levels; it is a late pro- 

 phase stage of an egg follicle cell before the chromosomes are 

 draw^n completely into one plane. 



Amphiscepa bivittata 



All this material came from larvae. The different stages are 

 shown in Figs. 295 to 304. The spermatogonial plates contain 25 

 chromosomes, two pairs of long ones, one pair longer than the 

 other (Fig. 295). In the rest stage, there are no m-chromosomes, 

 but two plasmosomes are present (Fig. 296). The first spermato- 

 cyte plate shows two large chromosomes, one larger than the other 

 (Fig. 297), corresponding to the two large pairs of the spermato- 

 gonium. The plasmosomes here persist into the metaphase (Fig. 

 298). The odd chromosome is quite small (Figs. 297, x, 298, x, 

 299, x) and does not divide in the first division. Chromosomes 

 a and b of the first spermatocyte retain their relative sizes in the 

 second spermatocytes, both those containing 13 chromosomes 

 (Fig. 300), and those with 12 (Fig. 301). 



PcEciloptera bivittata 



Poeciloptera bivittata very closely resembles the last described 

 species, even to the number and relative sizes of its chromosomes 

 (Figs. 305-313). It has two plasmosomes in the growth period, 

 and one or both of these persist in a most remarkable fashion even 

 to the anaphase of the second spermatocyte division (Fig. 312). 

 The size of the chromosomes and cells is greater than in Amphis- 

 cepa bivittata. 



