194 bulletin: museum of comparative zoology. 



A somewhat similar case is described by Strasburger (: 00), in wliich a 

 smut, Ustilago violacea, when present as a parasite in the female plant of 

 Melandryum album, causes the female organ of the latter, the pistil, to 

 remain undeveloped, while the anthers, normally mere rudiments, grow 

 to a large size and actually form pollen-mother cells, which the fungus 

 then attacks and destroys. In this case it is the male character which, 

 though normally recessive, is made to appear upon destruction of the 

 genital fundament of the opposite sex ; in the case of Carica papaya, it 

 is the female character which behaves in a similar way. 



Tlie objection may be offered that certain of the examples cited really 

 belong in the category of imperfect hermaphroditism, or at any rate of 

 potential hermaphroditism. This I freely grant ; I would even go 

 farther and say that all animals and plants are potential hermaphrodites, 

 for the;/ contain the characters of both sexes, but ordinarily the characters 

 of one sex only are developed, those of the other sex being latent or else 

 imperfectly developed. 



In true hermaphrodites, however, the characters of both sexes exist 

 fully developed side by side, as do the gray and the white coat-colors in 

 spotted mice. The true hermaphrodite, then, is a sex-mosaic ; to the 

 heredity of sex, in its case, we may expect to find applicable the 

 general principles of mosaic inheritance. 



The difference between a hermaphrodite and a dioecious animal is 

 precisely parallel to that which exists between a spotted and a normal 

 hybrid mouse. In the hermaphrodite, as in the spotted mouse, two 

 characters ordinarily alternative exist as co-ordinates, side by side ; in 

 dioecious animals, as in ordinary hybrid mice, the same two characters 

 exist in their more usual relationsliip of dominant and recessive. The 

 only difference between the two classes of cases is this. In coat-color 

 among mice gray is invariably dominant over, or balanced with white, 

 but never recessive toward it. But in dioecious animals the male char- 

 acter is sometimes dominant over the female, sometimes balanced with 

 it, and sometimes recessive toward it. This condition, though not paral- 

 leled in the illustration chosen (coat-color of mice), is not without a 

 parallel among other Mendelian cases. For,-Tschermak (:00) finds that 

 in certain crosses among peas, one charactev may be, with reference to 

 another, sometimes dominant, sometimes recessive. 



We have seen that spotted (hybrid) mice commonly produce gametes 

 which are, like themselves, mosaic, DR, whereas ordinary (gray) hybrids, 

 in which white is recessive, produce '* pure " gametes, either D or i?, in 

 accordance with the principle of segregation. Similarly the sea'-mosaic, 



