Agronomy and Horticulture Department


Date of this Version



Science, New Series, Vol. 59, No. 1521 (Feb. 22,1924), pp. 176-182


Copyright 1924 R. A. Emerson


It seems a conservative statement to say that studies

of the past twenty years among animal forms have

tended increasingly to link the phenomena of sex inheritance

with the behavior of chromosomes. To this

result, cytology and genetics have contributed perhaps

almost equally. The number of forms in which

one sex is known to have a morphologically different

chromosome complex from the other sex are many.

That, with respect to the chromosomes, the female of

certain forms produces gametes of a single kind,

whereas the male produces two kinds, and that in

turn an egg fertilized by one kind of sperm gives rise

to a female and with the other kind to a male, cytological

studies leave no doubt. In other forms it is

the female that produces two kinds of gametes and

the male one kind. The fact that in some animals sex

dimorphism is associated with unequal numbers of

chromosomes while in others, though the numbers are

the same, the sex chromosomes differ morphologically

in the two sexes, makes it seem not unlikely that functional

dimorphism may exist even where no morphological

differences in the chromosomes are seen.