Some Problems of Reproduction: a Comparative Study of ...

70 MARCUS M. HAETOG.
superBuities—all but indispensable to those that can obtain
them, not missed by those that have never known them, and
capable of being laid aside in time by a few of the former class.
Conversely, referring karyogamic rejuvenescence to mere constitutional
invigoration, we can see that agamy and apogamy
are harmless conditions where other modes of rejuvenescence
prevail. 1
C. ALLOGAMY AND SEX.
Again, if the invigorating effects of karyogamy be due to
the mere infusion of new blood into the firm " Cytoplast,
Nucleus, and Co.," it is, of course, an advantage that the new
blood should be as new as possible within the limits of possible
harmonious co-operation—that is, usually, within the bounds of
the race or species. And this must have been the cause which
determined exogamy in the lowest organisms. In this case
the members of a brood of gametes are incapable of entering
into fertile karyogamic union with one another, being affected,
as we may say, by the disqualification of consanguinity. This
disqualification has been attributed to a latent sexual differentiation
; but to admit this view is, as we shall see at once, to
deprive the word "sex" of the connotation of a differentiation
of organisms into two complementary categories.
For if exogamy implied any sexual differentiation in the
ordinary sense, and we considered any twenty-six broods of
gametes, say of Botrydium, they should fall into two categories,
which we will term A—M, N—Z respectively; any of
the gametes of the former category would be incapable of
forming fertile union with any other of its own category, but
would pair freely with any of the other, and vice versa. But
1 It is interesting to note that Ferns, which are dimorphic, have a resting
state (spore) interposed between the terrestrial Fern-plant and the palustrine
prothallus, asexual karyogamic union between the palustrine and the terrestrial
states. In some exceptional cases the one or other transitional form of rejuvencsceuceis
omitted: in apospory the paluslrine form supervenes without the
resting state of spores ; and in apogamy the terrestrial state supervenes without
karyogamic rejuvenescence : but a combination of these two phenomena is
uot known in the samespecies, or I think I may say the same group.