196 HEREDITARY CHARACTERS 



very suggestive with regard to Wilson's theory. In these 

 particular cases it has been shown that the unfertilised eggs 

 produce males, the fertilised eggs females. But it has also 

 been shown that half the cells destined to be converted into 

 sperms in the males, degenerate and never fertilise the ova. 1 

 It is also stated that the cells that degenerate are those that 

 lack the supernumerary chromosome. Wilson claims that 

 the functional sperms must therefore all produce females. 

 Tempting as this theory is, it is impossible at present to 

 accept it unreservedly. Among the vertebrates, where the 

 production of sperms has been extensively studied, there is 

 no evidence whatever for two kinds of sperms or for the 

 existence of an accessory chromosome. In some animals 

 it has been shown that there are two kinds of eggs, 2 and 

 it has been suggested that the process in these cases may 

 be reversed, the accessory chromosome being present in 

 some of the eggs but not in the others. Among vertebrates 

 we have no evidence for two kinds of eggs, although the 

 process of ovigenesis has not been so exhaustively studied 

 as that of spermatogenesis. 



It is necessary to point out that the existence of the 

 accessory chromosome has been disputed, even in one of 

 the organisms employed by Wilson, and observations upon 

 other insects suggest that there may be a certain amount of 

 misinterpretation on this point. 3 Both parties have repeated 

 their observations and still remain in disagreement. Ex- 

 haustive observations upon the maturation of the eggs of an 

 insect closely allied to the subjects of the observations of 

 Wilson and his supporters, upon the eggs of an earthworm 

 (Allolobophora), and upon the spermatogenesis of other 

 insects, suggest very strongly that the interpretation of 



1 Meves, F., " Die Spennatocytcnteilungen bei der Honigbicne, nebst 

 Bemerkungen iiber Chromatinreduktion, Arch. f. mikr. Anat., Ixx , 1907; 

 Morgan and von Baehr, quoted by Wilson, Science, vol. xxix., No. 732, 1909. 



2 e.g. Rotifers, see p. 193. 



8 Foot, K., and Strobell, E. C. , "The Accessory Chromosome of Anasa 

 tristis," Biol. Bull., xii., 1907; "A Study of the Chromosomes in the Sper- 

 matogenesis of Anasa tristis," Am. Journ. Anat., vii. 2, 1907. 



