HEREDITY I 89 



into two well-defined groups, and we are logically forced to the con- 

 clusion that the pecuhar chromosome has some bearing upon the 

 arrangement. 



"I must here also point out a fact that does not seem to have the 

 recognition it deserves ; viz. that if there is a cross division of the chro- 

 mosomes in the maturation mitoses, there must be two kinds of sper- 

 matozoa regardless of the presence of the accessory chromosome. It 

 is thus possible that even in the absence of any specialized element 

 a preponderant maleness would attach to one half of the spermatozoa, 

 due to the 'quahtative division of the tetrads'"* 



McClung was incHned to believe that that half of the spermatozoa 

 which contains the accessory chromosome gives rise to male offspring, 

 while the other half gives rise to female offspring. 



E. B. Wilson f has recently investigated the chromosomes of the 

 sex cells in a number of Hemiptera, and ascertained that the occur- 

 rence of two kinds of spermatozoa is a constant phenomenon in this 

 group. While in some forms the two kinds differ by an accessory chro- 

 mosome occurring in one half of the spermatozoa of a male, in other 

 forms they differ in regard to the size of one of their chromosomes. 

 In the latter forms this specific "idiochromosome" is large in one half 

 of the spermatozoa of a male and small in the other half of the sperma- 

 tozoa. While McClung assumed that the accessory chromosome is 

 a determinant for the male sex, Wilson shows that it is more probable 

 that it gives rise to the female offspring. 



If we sum up all these data concerning determination of sex, we 

 therefore come to the conclusion that sex is, in all probability, already 

 predetermined in the sex cells. In some forms, e.g. Aphides and other 

 parthenogenetic forms, sex can unquestionably be determined by the 

 eggs alone, and consequently we must assume here the existence of 

 two kinds of eggs. In other organisms, like the Hemiptera and Or- 

 thoptera, we have two kinds of spermatozoa and apparently one kind 

 of eggs, and in these cases it is the spermatozoon which determines the 

 sex. There exists apparently a third type of forms, e.g. bees, ants and 

 social wasps, in which both eggs and spermatozoa share in the deter- 

 mination of sex, inasmuch as the eggs alone determine the male, while 

 the spermatozoon determines the female sex; if both are united, the 

 influence of the spermatozoon predominates. If this is correct in this 

 group of animals, only one kind of eggs and only one kind of sperma- 

 tozoa will be found, t 



* McClung, he. cit. 



t E. B. Wilson, Science, N. S. Vol. 22, p. 500, 1905. 



j It follows from these data that the female egg, or spermatozoon, predetermines 

 also a different group of instincts from the male egg. Morphologically as well as in regard 



