SPERMATOGENESIS OF THE CHICKEN 67 



had an explanation offered for them in the above paragraphs, 

 but there are some cells such as figures 10, 14, 28 c, 53 and 61 

 where there is a distinctly separated piece of chromatin. It 

 seems, however, a reasonable explanation that these are one, two, 

 or several of the ordinary chromosomes that happen to be too 

 far from the others to fuse into the general mass. If this ma- 

 terial were such that one could count the number of chromosomes 

 in the first and second spermatocytes, and see tetrads formed for 

 division, one could tell absolutely whether the pieces were extra 

 chromosomes or not. But the chromosomes act almost as though 

 they were sticky on the surface, and those that happen to touch 

 each other stick close together and stain as though fused. Com- 

 paring figure 53 with 38 it is clear that the right hand piece is no 

 further from the center of the mass in the first than in the second 

 case, only it is one of the smaller chromosomes and therefore 

 did not touch the mass and stained separately. If one com- 

 pares figures 52 and 40, the same thing-is seen: the rod is a little 

 shorter and does not quite touch the mass in 52, while it just 

 touches it in 40. 



A study of all the photographs of the primary spermatocyte 

 equatorial plates as shown on plate 1 and all the drawings of 

 the same stage, as shown on plate 4, in the order in which they 

 are arranged on the page will show a gradual transition from the 

 large mass with projecting arms, through the smaller mass with 

 separate chromosomes nearby or even touching, to the small 

 mass with chromosomes quite far away. A similar study of the 

 series of photographs and drawings of the side views of the meta- 

 phase spindles of the first spermatocytes, as shown on plates 2 

 and 5, indicates the same sort of transition. 



The difference in size of these chromosomes left outside of the 

 general mass in different cells, would indicate a regular and con- 

 stant size difference among the chromosomes. Some of the clear- 

 est aceto-carmine preparations give additional evidence for this 

 (figs. 87, 89, 90, 91). In these preparations it was more clearly 

 possible to see all the separate chromosomes than in prepara- 

 tions by any other technique. But even here counting proved 

 illusory. Figure 86 shows six chromosomes, figure 87 seven, 



