CHROMOSOMES OF HUAIAN SPERMATOCYTES 5 



2. The remaining 22 spermatogonia! chromosomes lose their 

 distinctness of outline in the early part of the growth period 

 to emerge later as 11 bivalent chromosomes in the prophases 

 of the primary spermatocyte. 



Figines 21, 22 and 23 represent side views of the primary 

 spermatocyte division in which at either end of the spindle are 

 seen two unequal chromosomes very closely placed if not ac- 

 tualty united (Xi Fi, X^ Y^) which I believe are the products 

 of the divided XF ot the preceding figures. In these cases 

 each ekment of the XY has divided longitudinally considerably 

 in ad^'ance of the division of the remaining 11 chromosomes. 

 The early division of the A^F is not an invariable rule as may be 

 seen from figure 25 in which one of the other chromosomes has 

 divided into 6i and 62 before the others. In other cases as in 

 the anaphase pictured in figure 27 it is impossible to pick out 

 the XY or its division products. In figure 26 two chromosomes 

 are shown dividing in advance into Ci Co and di, do,. It may be 

 that in this case X and F elements became separated before 

 dividing or it may be that two of the ordinary chromosomes 

 have divided. Figure 28 is an anaphase in which the XY moie- 

 ties can be distinctly seen well in advance of the other chromo- 

 somes. Figures 21, 22, 26 and 28 are from negro testes; figures 

 23, 24, 25 and 27 from white. 



Figure 29 (white) shows an oblique view of an anaphase in 

 which every chromosome has divided. The dotted line ah sepa- 

 rates the two daughter groups each of which contains 12 chromo- 

 somes. In this case the m chromosome is the last to divide. 

 The products of XY are shown at A^Fi, and A^Fo. Figure 30 

 shows the same stage in the negro. Here likewise the dotted 

 line ah is the line of demarcation between the two daughter 

 groups each containing 12 chromosomes. In the telophase 

 stage of figure 31, it is possible to count 12 chromosomes at the 

 left pole — the right pole being not entirely clear owing to fusion 

 of the chromosomes. In figure 32 a large plasmosome (P) is 

 seen near one pole. Without proper precautions in staining 

 this body might be mistaken for a chromosome. 



