THE CELLULAR BASIS 153 



by a sperm with 23 chromosomes an individual 

 with 47 chromosomes, or a male, results 

 (Fig. 37). 



It must be said that other investigators, 

 notably Guyer and Montgomery, have not 

 found 47 chromosomes in the spermatogonia 

 of man, but about 22. Since both the latter 

 investigators worked on negroes whereas Wini- 

 warter worked on white men it has been sug- 

 gested quite recently by Morgan and Guyer 

 that there may be twice as many chromosomes 

 in the white race as in the black. A similar con- 

 dition in which one race has twice as many 

 chromosomes as another race of the same 

 species is found in two races of the thread 

 worm, Ascaris megalocephala* 



Similar correlations between chromosomes 

 and sex have been observed in more than one 

 hundred species of animals belonging to widely 

 different phyla. In a few classes of animals, 

 particularly echinoderms and birds, the evi- 

 dence while not entirely convincing seems to 

 point to the fact that two types of ova are 



*Still more recent work by Wieman shows that the number 

 of chromosomes in white men and in negroes is 24; in the male 

 there is presumably an XY pair, in the female an XX pair. 



