THE CELLULAR BASIS 147 



It must be said that other investigators, 

 notably Guyer and Montgomery, have not 

 found 47 chromosomes in the spermatogonia 

 of man, but 22. Since both the latter investi- 

 gators worked on negroes whereas Winiwar- 

 ter worked on white men it has been suggested 

 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, but it is still too 

 soon to affirm that this is true of white and 

 black races of man. 



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 

 produced and but one type of spermatozoa; 

 but the general principle that sex is determined 

 by the chance union of male-producing or fe- 



