324 7. H. Morgan 
bearer of the female character, is weaker than F, or in modern 
terminology, the dominant F has become a,recessive F’ (with 
respect to M), the results can be accounted for. Expressed in 
phylogenetic terms, originally only one kind of individual devel- 
oped as a result of union of F and M. Gradually two kinds of 
individuals arose owing to one of the / determinants becoming 
weaker than its opponent, M. In time this / became smaller or 
vanished, because it lost all real function except as the bearer of 
latent female characters in the male. In other words whenever 
four sex chromosomes exist the male carries potentially (recessive) 
the female characters, wherever the fourth chromosome has dis 
appeared, as in certain insects and spiders, the male is a homo- 
zygous male. ‘This scheme is advanced merely i in order to show 
how, on the chromosome theory, the graded series shown by the 
fourth chromosome might be consistently worked out. ‘The view 
assumes both reciprocal fertilization and sex primordia that “segre- 
gate’ in the gametes. It ignores the fact that no differences 
between F’ and F have been seen. It assumes that sex primordia 
exist both in males and females and that there are two classes of 
males in different species, some pure males, others mixed. It 
encounters the objections that may be raised against the view 
that the egg determines 77 all cases the sex, because it contains the 
dominant male and female primordia. 
The problem is simplified if we assume that the three chromo- 
somes are identical, in which case the result is quantitative. 
Femaleness is only twice maleness in the sense that when one of 
the three bodies is present a male develops, when two a female. 
It may be urged in opposition to this conclusion (1) that the female 
may develop male characters; (2) that the difference between the 
male and the female characters may depend on qualitative differ- 
ences as shown by injecting sperm extracts into the female that 
call forth male characters; (3) that in mosses the male and the 
female may develop with half of the chromosomes present; (4) 
that in the phylloxerans the producers of male eggs and female 
eggs appear with the full number of chromosomes present; (5) 
that the function of the mate of the accessory when it is present is 
ignored. ‘These objections may possibly be met by the following 
considerations: 
