Sex Determination in Phylloxerans and A phids 25 
1 The female develops male characters (by which is meant 
secondary sexual characters not spermatozoa) in old age or after 
castration. ‘his may mean that these secondary characters owe 
their suppression in the female to materials manufactured in the 
ovaries. In insects, however, it has been found that the secondary 
characters of the male do not appear in the female after castra- 
tion. Gynandromorphism, that occurs in this group, may depend 
on a different relation and will be considered later. 
2 The primary qualitative differences between the sexes have 
never been changed by injection, They represent the fundamen- 
tal alternatives of the protoplasm and quantitative factors only 
determine which alternative is realized. ‘The secondary charac- 
ters of the male that arise in the female by injecting male extracts 
can be explained if the injected substance overcomes the inhibiting 
effects produced by the products of the ovary. 
3 In mosses only one kind of sporogonium exists, hence as 
pointed out, the case is not parallel. Waiving this distinction, the 
problem inthe mosses is concerned with the development of two 
kinds of gametes which may depend on some unknown quantita- 
tive relation existing in the reduced groups of chromosomes—if 
chromosomes here represent the material factor of sex determina- 
tion. 
4 In the phylloxerans all the chromosomes are present when 
the male and the female egg develop, yet a change in their grouping 
has been demonstrated in one case at least. Whether this in itself 
will account for the result is not evident, but the change is con- 
cerned with the production of two kinds of eggs not necessarily 
with the production of male and female. ‘The male develops only 
after two chromosomes are extruded. 
5 When the mate of the accessory is the same size as the acces- 
sory—in other words when no accessory exists—we have no obvi- 
ous difference in the chromosomes by which to explain sex. Yet 
differences may exist that have not yet been found, as Boveri has 
shown, in the case of the sea urchin. Until such facts become 
known, however, this is a real objection to the quantitative inter- 
pretation, and unless such facts are discovered it is fatal. The 
absence of data on this point is not due to lack of observations, 
