476 THE REPRODUCTIVE SYSTEM 



or accessory chromosome appears in the male, or where its representative 

 is an odd group. Cases are known among insects, where the homologue of 

 the accessory may have a mate of smaller size (or possibly even equal size, 

 but of typical allosome behavior idiochromosomes), or where the accessory 

 representative may be an even group, in which instances the numerical rela- 

 tionships are different, but the principle of sexual relationship remains the 

 same. 



Confining our attention then to the simplest case, as illustrated in our 

 specimen of the grasshopper, we may note that all the cells of the female, 

 including the oogonia, contain 24 chromosomes. Two of these correspond 

 in size to the accessory of the male group, which group in all soma cells 

 and all spermatogonia comprises 23 chromosomes. We recall that one-half 

 of the spermatozoa received 11 chromosomes, the other half 11 plus the 

 accessory, or 12 chromosomes. All mature eggs contain 12 chromosomes. 

 When therefore a spermatozoon with 11 chromosomes fertilizes an egg with 

 12 chromosomes, the resulting organism will have 23 chromosomes, and 

 become a male; when, on the contrary, a spermatozoon with 12 chromo- 

 somes fertilizes an egg with 12 chromosomes, the organism will have 24 

 chromosomes and become a female. 



An essentially similar relationship is now known to obtain in many 

 forms, chiefly insects, but including also various vertebrates, even mam- 

 mals and man. According to Winiwarter (Arch, de Biol. T. 27, 1912), the 

 white human male produces spermatozoa of two sorts, one with 23 chro- 

 mosomes, the other with 24 ; the male cells containing 47 chromosomes, the 

 female 48. There is some uncertain evidence to indicate that the negro 

 has half the number of chromosomes possessed by the white man, the 

 mulatto consequently possessing numerically intermediate groups. 



With regard to the function of the accessory chromosome in relation 

 to sex determination, two obvious possibilities present themselves: (1) it 

 may qualitatively determine sex, that is, carry the determiner upon which 

 sex depends; (2) it may act in a quantitative way, that is, sexual differ- 

 ence may depend upon differences in the amount of chromatin. On the 

 contrary the presence of one accessory in the male, arid two (homologues) 

 in the female may be simply accompaniments of sex in a sense somewhat 

 similar to secondary sexual characters (e. g., combs and spurs in poultry), 

 these as well as other sexual differences being in common dependent upon 

 some more recondite fundamental sex 'determiner.' Experimental evidence 

 tends increasingly to show that all organisms carry the potentialities of 

 both sexes, and that sex differences are largely differences in degree of dif- 

 ferentiation ; in other words, that femaleness represents an inhibited male. 

 The greater amount of chromatin in the female, due to the presence of 

 two sex chromosomes as against one in the male may be conceived to 

 inhibit the higher grade of differentiation demanded by maleness. 



Attempts have frequently been made recently somehow to bring sex 



