222 7. H. Morgan 
In other words, the sex of the gametes as applied to conjugation has 
been merged into the sex problem of the sporophyte. At the pres- 
ent time, in fact, several recent theories of sex, as in Castle’s 
latest view, do not hesitate to make a male gamete (sperm) fertilize 
a male gamete (egg). We meet here with an apparent contradic- 
tion in terms by using the same words, male and female, for the 
higher and the lower forms. ‘The results can be harmonized if we 
admit that by sex in higher animals and plants we refer to a differ- 
ent condition from the s/gn of the gametes concerned in the act of 
fertilization. All sperm must then be of one sign (+ or —), all 
egos of the opposite sign (unless reciprocal fertilization beassumed). 
But on the view that the female (or the male) is heterozygous in 
regard toits gametes, i.e.,a + (ora —) gamete may carry either a male 
or female sporophore-determinant, what then determines the sign 
of the gametes? This question is left unanswered or ignored. 
Evidently the result cannot depend on its association with the male 
or the female since no such relation is recognized on this view. 
MENDELIAN TREATMENT OF THE SEX PROBLEM 
The presence in animals and plants of two kinds of individuals, 
males and females, has led to several attempts to explain their 
presence according to Mendel’s Law. Sex is treated as a unit 
character not different from other unit characters in its heredity. 
Correns’ experiments give the best basis for an explanation along 
these lines. The more speculative writings of others will be con- 
sidered later. 
Bryonia alba is moncecious; Bryonia dioica is dicecious. 
1 When the female plants of dioica were fertilized with pollen 
from alba all the plants were female. Correns concludes from this 
result that the dicecious condition (with only one sex on one plant) 
dominates the moncecious condition; and since the resulting 
plants are always of the same sex, the eggs through which the 
dicecious condition was introduced must have been all of one kind 
—female producing. 
2 The normal combination of B. dioica 9 x dioica # pro- 
duces females and males in equal numbers. The result shows 
