6 HUMAN SPERMATOGENESIS: A STUDY OF INHERITANCE. 



case, one of the daughter secondary spermatocytes would receive D and a half 

 of d y the other would receive only a half of d. 



Condition D, the smaller allosome, d, at one pole, none at the other, D being 

 then probably in the equator. This was seen in 5 cases (fig. 23) . In this condi- 

 tion D probably divides in the equator along with the other chromosomes, con- 

 sequently one daughter cell would receive d and a half of Z), and the other would 

 receive a half of D. 



Condition E, both D and d divide equationally, found in 3 cases. This is 

 seen distinctly in fig. 25; in fig. 24 the spindle is very oblique, causing the two 

 dividing allosomes to appear nearer one pole than they really are. Each second- 

 ary spermatocyte would then receive a half of D and a half of d. 



The remaining conditions concern variations in the distribution of the ordi- 

 nary chromosomes. 



Condition F, one entire undivided geminus at one spindle pole, found in 3 

 cases (fig. 26, PL II). In the case figured both allosomes are at the same pole. 

 Following division of such a cell one secondary spermatocyte should receive 

 two more dyads than the other. 



Condition G, one geminus dividing precociously so that one dyad lies at one 

 pole and one dyad at the opposite pole, found in 3 cases. Fig. 27 illustrates 

 this condition; in the left hand cell both allosomes are at one pole, a combination 

 of conditions A and G; in the right hand cell both allosomes have divided, so that 

 at each pole there is a half of a geminus, a half of D and a half of d. This condi- 

 tion G is only a slight variation, a precocious division of a geminus, it cannot 

 lead to any change in the number of dyads in the secondary spermatocytes. 



The anaphase of the first maturation mitosis is drawn in fig. 28, telophases 

 in figs. 29-33, showing that a marked interkinesis or rest stage follows this 

 division. In the stages of figs. 32, 33 compact bodies are found within the 

 nuclei of the daughter cells, secondary spermatocytes. These bodies are not 

 fixed in number, some being allosomes and some plasmosomes, as can be deter- 

 mined by the Ehrlich-Biondi stain. The preparations from which these figures 

 are made were stained by iron-hsematoxyline, which does not give a staining 

 difference between the two kinds of bodies. 





2. Secondary Spermatocytes, 



Late prophases of the second maturation mitosis are shown in figs. 34-36, 

 PL II, in each of which all the chromosomes are shown. Figs. 34 and 35 show 

 each 12 chromosomes and each probably contains two allosomes, fig. 36 exhibits 

 1 1 chromosomes and therefore probably contains only one allosome. 



Two polar views of second maturation spindles are given in figs. 37, 38, the 

 former showing 10 chromosomes, the latter 12; the latter contains the allosomes 

 D, d, lacking in the former. The ordinary chromosomes are here well marked 

 dyads, appearing longitudinally cleft; they are quite different in appearance 

 from the heavier chromosomes of the previous mitosis (fig. 13). Several vari- 

 ations can be distinguished in the mode of division of the chromosomes: 



