then, was inheritance definitely traced to the nucleus. If
this nucleus is a male the characters are those of the male line; if a
female those of the female line, and in sexual reproduction where the
two are fused, half and half.

Yet the fact remained that all efforts to develop the spermatozoon alone
(without the agency of any egg material at all) into an individual had
signally failed. Conklin[11] had found out in 1904 and 1905 that the egg
cytoplasm in Ascidians is not only composed of different materials, but
that these give rise to definite structures in the embryo later on. So a
good many biologists believed, and still believe[12,13,14] that the egg
is, before fertilization, a sort of "rough preformation of the future
embryo" and that the Mendelian factors in the nuclei "only impress the
individual (and variety) characters upon this rough block."

If we look at these views from one angle, the apparent conflict
disappears, as Professor Conklin[15] points out. We can still presume
that all the factors of inheritance are carried in the nucleus. But
instead of commencing the life history of the individual at
fertilization, we must date it back to the beginning of the development
of the egg in the ovary. Whatever rude characters the egg possesses at
the time of fertilization were developed under the influence of the
nucleus, which in turn got them half and half from its male and female
parents. These characters carried by the female across one generation
are so rudimentary that they are completely covered up, in the
developing embryo, by those of the new nucleus formed by the union of
the sperm with the egg in fertilization.

In case fertilization does not take place, this rude beginning in the
egg is lost. Since no characteristic sex is assumed until after
fertilization, we may say that life begins as neuter in the individual,
as it is presumed to have done in the world. It will occur to those
inclined to speculation or philosophic analysis that by the word
"neuter" we may mean any one or all of three things: (a) neither male
nor female; (b) both male and female, as yet undifferentiated, or (c)
potentially either male or female. Clearly, the above explanation
assumes a certain _germinal_ specialization of the female to
reproduction, in addition to the body specialization for the
intra-parental environment (in mammals).

A tremendous amount of laboratory experimentation upon animals has been
done in late years to