12 HUMAN SPERMATOGENESIS: A STUDY OF INHERITANCE. 



Such reasoning would account satisfactorily for the number of allosomes 

 found in human males, as well as for the postulate that all four classes of sperma- 

 tozoa are capable of fertilization. But if it be correct it would not explain the 

 numerical sex ratio in man, where the males are more numerous than the 

 females. For if three of the four classes of spermatozoa are female-producing, 

 there should be more females than males. Also if there be only two classes of 

 sperm capable of fertilization, as Guyer argues, and one kind of egg, this should 

 result in equal numbers of the sexes and not in the ratio actually known. 3 



This analysis seems to be as far as we can go at present, yet it is entirely specu- 

 lative and unsatisfactory because we understand nothing of the chromosomal 

 relations in the female. It, however, does indicate strongly one important con- 

 elusion, that in man the male is heterozygous, the female, homozygous. 



What appears to be of much more importance is the establishment of the fact 

 of real intra-individual germinal variation. This variation in the spermatocytes 

 concerns principally the two allosomes, in lesser degree the ordinary chromosomes. 

 Instead of reasoning deductively that such variation must occur, the actual 

 evidence of its occurrence is increasing, and such phenomena will in time furnish 

 the basis of our understanding of variation. 



A second important point needs mention. Bardeleben held that a second 

 reduction of the chromosomes occurs in the secondary spermatocytes, resulting 

 in approximately a quarter of the normal number in the spermatids. Guyer 

 found about the same result, concluding of the secondary spermatocytes that 

 " half of them show five and the remainder seven chromosomes. A second pairing 

 of the ordinary chromosomes has evidently occurred, so that there are five 

 bivalent chromosomes in each type of cell and the additional two accessories in 

 the one type." I have seen no evidence of any kind of such a pairing of chromo- 

 somes in the secondary spermatocytes, neither in my own material nor in that 

 received from Guyer, though I have examined fully two hundred division stages 

 of these cells. Of decisive value are such cases, of which several are figured by 

 me, where all the chromosomes can be distinctly seen on lateral views of spindles 

 of the second maturation. The only explanation I can offer for this conflict of 

 opinion is that Bardeleben and Guyer either employed too intense staining of 

 their sections, or else studied cells in which the chromosomes had been greatly 

 swollen by fixation and hence were not clearly distinguishable. In fact, those 

 fixed by Zenker's fluid appeared far more distinct and separate than those pre- 

 served in either Bouin's or Gilson's fluid. 



1 Attention may be again called to the fact that in a number of species of animals males and 

 females do not occur in equal numbers, yet equal numbers should result if the allosomes alone are 

 sex determinants. 



