D. W. Cutler 157 



Spermatogenesis of tlie Pheasant. 



The spermatogenesis of the pheasant is exceedingly difficult to eluci- 

 date, iiwing to the tendency of the chromosomes to stick together, thus 

 making it very hard to separate one from another, also the linin of the 

 nucleus takes up the stain, though not to the same extent as the 

 chromosomes, making clear figures very difficult to find. 



I have examined many sections of the testes, but in no case has it 

 been possible to determine the exact number of chromosomes in the 

 spermatogonial cells. It has frequently happened that the chromosomes 

 were all separated one from another, with the exception of one or two, 

 which were so closely associated that it was impossible to decide the 

 exact number representing the complex. However, from the examination 

 of many spermatogonial division figures I conclude that the chromosome 

 number is from twenty to twenty-two. Fig. 1 shows very well the 

 appearance which most of the spermatogonial cells have when seen in 

 polar view. When viewed from the side they appear quite typical in 

 character. 



Primary Spermatocytes. The growth of the spermatogonia into 

 primary spermatocytes is initiated by the nucleus increasing a little in 

 size ; the chromatin is scattered through it in the form of small granules 

 lying on a fine network (Fig. 2). The next stage is the formation of a 

 thin spireme, which gradually contracts to form the synizesis stage in 

 which the threads jaass into a tangled condition. It is very characteristic 

 of this stage to find the chromatin threads aggregated together at one 

 side of the nucleus (Fig. 3). I have not been able to follow the details 

 of this process or to detprmine in what manner the bivalent chromosomes 

 arise. The next stage, which immediately follows .synizesis, is shown in 

 Fig. 4 where the threads fill the whole of the nucleus and are thickened. 

 The question of the number of double chromosomes that arise fi-om these 

 threads is again exceedingly difficult to decide. In most cases the 

 number appears to be either 10 or 11, but even in the best of the figures 

 one cannot be absolutely certain. The arrangement of the chromosomes 

 is, however, characteristic. In polar view there is seen a ring of chromo- 

 somes with one or two lying in the centre (Figs. 5, and 6). Also it is 

 common to find one of the chromosomes protruded far outside the others, 

 making it a very conspicuous element. Fig. 6 exhibits this well and 

 corresponds very closely with some of the figures published by Uuyer in 

 his recent paper on the chromosomes of the fowl. 



11—2 



