DAVIS: SPERMATOGENESIS. 73 



the middle of the concave side of the nucleus. This is of considerable 

 interest, since in the early stage of the primary spermatogonia the 

 monosome usually occupies a similar position. 



As the chromosomes disintegrate during the telophase they are, 

 in general, oriented with their long axes parallel to a line extending 

 through the two poles of the cell. During the resting stage all traces 

 of chromosomal limits disappear, but in the succeeding prophase, 

 when the chromosomes reappear, they have the same orientation as 

 in the telophase of the preceding di^•ision. Obviously, the most plau- 

 sible explanation of this is that during the resting stage the chromo- 

 somes still retain their individuality, although they are not recognizable 

 as distinct bodies. Otherwise, it is difficult to see why they should 

 reappear with the same orientation as before. Somewhat similar 

 phenomena have been described by Rabl ('85) and Boveri ('88). 



B. Arphia tenebrosa. 



The spermatogonia and apical cell are approximately as in Dissos- 

 teira. Figure D (p. 72) is a polar view in the equatorial-plate stage 

 showing, as in Dissosteira, twenty-three chromosomes. These can be 

 easily arranged in pairs, but in this species there are four large pairs; 

 the next smaller chromosome is unpaired, the monosome, and this is 

 followed by a series of five nicely graded pairs of diminishing sizes. 

 There is, as in Dissosteira, a greater difference in size between the 

 smallest of the medium sized chromosomes and the two smallest pairs , 

 than between the successive sizes of the other chromosomes. 



C. Hippiscus tuberculatus. 



The spermatogonia present no essential differences from those of 

 Dissosteira. The apical cell, however, differs somewhat in appearance, 

 there being in most cases no deeply staining granules in the cytoplasm. 

 Usually there is around the nucleus simply a very finely granular 

 material, which is comparable to that seen in Dissosteira, but stains 

 much less deeply. Moreover, the granular material is distributed 

 equally on all sides of the nucleus. In this species the primary sper- 

 matogonia usually do not entirely surround the apical cell, which con- 

 sequently is in contact on one side with connective-tissue cells. 



In the metaphase twenty-three chromosomes can be distinguished 

 Avhich, as in the preceding species, vary greatly in size. Figure F, 

 which is a polar view in the equatorial-plate stage, shows that here, 



