2, tee BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
VI. Summary. 
1. Sex is an attribute of every gamete, whether egg or spermatozo6n, 
and is not subject to control through environment. It is inherited in 
accordance either with Mendel’s law of heredity or with the principle of 
mosaic heredity. 
2. Mendel’s law includes two principles, (1) the principle of domi- 
nance in heredity of one of two alternative characters over the other, and 
(2) the principle of segregation of those characters at the formation of 
the gametes. 
3. Mosaic inheritance is an important exception to both these prin- 
ciples. In this process alternative characters coexist without domi- 
nance of either, and pass together (without segregation) into the 
gametes. 
4. The Mendelian principles of dominance and segregation apply to 
the heredity of sex among dioecious animals and plants, but among 
hermaphroditic animals and plants mosaic inheritance of sex takes 
place. 
5. Latency of one sex in the other, among dioecious animals and 
plants, is shown by evidence both anatomical and experimental. 
6. Segregation of sex, among the gametes of dioecious animals and 
plants, is accompanied by morphological differences between the male 
and female eggs in Dinophilus and certain Lepidoptera, and possibly 
also by dimorphism among the spermatozoa of Paludina. 
7. Among dioecious animals, a gamete of one sex can unite, in fertili- 
zation, only with one of the opposite sex; consequently no individuals 
are produced from fertilized eges, which are purely of one sex or the 
other. 
8. Dominance, in dioecious species, is possessed sometimes by the 
male character, sometimes by the female. 
9. In parthenogenetic species, the female character invariably domi- 
nates, when the characters of both sexes are present together. Accord- 
ingly in such species : (a) All fertilized eggs are female. (%) Unfertilized 
eggs which are produced without segregation of the sex-characters are 
female. (c) Males develop only from unfertilized eggs from which the 
female character has been eliminated. 
10. The female character, eliminated from the male parthenogenetic 
ego, passes into the testis ; accordingly the spermatozoa bear the femade 
character, though the individual producing them is in soma purely 
male. 
