THE GENERAL ASPECTS OF HEREDITY 21 



chromosomes which divide in the first reduction 

 division and segregate in the second, unUke the other 

 chromosomes which segregate in the first and divide 

 in the second. Still more recently, Painter (1921), 

 in a preliminary account of spermatogenesis in both 

 whites and negroes from Texas, finds approximately 

 48 chromosomes in both, including an XY pair of 

 sex chromosomes. This is a partial confirmation of 

 Von Winiwarter. It might appear that all these 

 investigators were right in their determinations of 

 numbers, and that human individuals exist with 

 24 (2X or diploid), about 36 (3X or triploid), and 48 

 (4X or tetraploid) chromosome numbers. The chro- 

 mosomes of all mammals are, however, notoriously 

 difficult to deal with, and it seems more likely that 

 clumping may have given rise to an appearance of 

 lower numbers. The existence of triploid and tetra- 

 ploid races of mankind would, however, be in accord 

 with their occurrence in man}^ species of plants and 

 animals (see Gates, 191 5, pp. 195 ff.). In an}^ case, 

 it seems clear that the higher number (48) of chromo- 

 somes is present at least in some men, and that an 

 XY pair of chromosomes exists in the male. 



It may be pointed out that the number 48 is a rather 

 high one, and is approximately double the number 

 found in some mammals.* It has, therefore, probably 

 originated at some time by sudden doubling of the 

 chromosome number, as this was originally shown 

 to take place when CEnothera gigas appears as a 

 mutation from CE. Lamarckiana (see Gates, 191 5, 

 pp. 118, 209). Whether this doubling to produce 

 48 chromosomes occurred in some of the races of 

 mankind, or earlier in his ancestry, remains to be 

 determined. In the matter of relationships and 

 phylogeny, as has recently been shown, in the varieties 



* Painter (1922) reports finding 54 chromosomes, including 

 an XY pair, in a ring-tail monkey. 



