HUMAN SPERMATOGENESIS: A STUDY OF INHERITANCE. 



Condition a, all chromosomes divide at the plane of the equator, found in 

 104 cases. This is shown in figs. 38-41, of which all but the last exhibit the total 

 number of chromosomes (12). The allosomes are probably those lettered D 

 and d. This condition must have followed conditions A or B of the primary 

 spermatocytes. Fig, 41 shows an unusually small secondary spermatocyte, but 

 all grades in size are to be found between it and such a large cell as fig. 47. 



Condition 6, like the preceding condition, but the allosomes dividing pre- 

 cociously as exhibited in fig. 42. This was found in two instances. In coi li- 

 tions b and a the daughter cells, spermatids, would receive precisely equivalent 



chromosomes. 



Condition c, one split chromosome, polar-lateral from the others, found in 



only one case and drawn in fig. 43. (This figure shows all 12 chromosomes.) 



This misplaced chromosome is probably d } and should it be transmitted entirely 



to one spermatid, that cell would receive an entire allosome that had not divided. 



Condition d, one chromosome to the side of the equator (fig. 44), found in one 



case. This displaced chromosome would seem not to be an allosome, judging 



by its size. 



Condition e, an unsplit allosome at one pole of the spindle, found in 19 cases. 

 Sometimes (fig. 45) this body appears to be D, judging from its size, in other 

 cases (fig. 46) to be d. These cases evidently result from condition C or I) of 

 the primary spermatocytes; and of the spermatids resulting, half would have 

 one allosome (either %D or }^d) and half would have none. 



Condition f, three unsplit chromosomes at one pole, none at the other (fig. 47), 

 found in one case. It is difficult to explain this except by assuming that two 

 of these bodies are the separated halves of one allosome (a further step in condi- 

 tion c), while the third is the other allosome (as in condition e). Following 

 such a division one spermatid would get no allosomes, the other spermatid 

 would get one part of one allosome and both parts of the other allosome. 



Condition g, one unsplit allosome at one pole, another unsplit allosome at the 

 opposite pole (fig. 48), observed in one case. This must have followed a first 

 maturation mitosis where both allosomes divided in the equator; and it would 

 result in giving to one spermatid a half of the larger allosome (D), and to the 

 other spermatid a half of the smaller allosome (d). 



The following conditions of variance refer to the ordinary chromosomes: 



Condition h I, one entire dyad at one pole (fig. 49), seen in 9 cases. This 

 would result in one spermatid receiving two monadic chromosomes more than 

 the other spermatid. 



Condition h 2, two dyads, of different sizes, at one pole (fig. 50, PI. Ill), 

 observed in 2 cases. Here one spermatid would receive four monadic chromo- 

 somes more than the other spermatid. 



Condition h 3, correspondent dyads at opposite poles of the spindle (fig. 51), 

 noted in 1 case. This must have resulted from a case of condition F (fig. 26) 

 of a primary spermatocyte, where an entire tetrad passed undivided to one pole, 



