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

SOME PROBLEMS OF REPBODTJOTION. 63
(e) The non-utilisation of all the cytoplasm in the elaboration
of the flagellate (or ciliate) spermatozoon from a tissuelike
cell, leaving anon nucleated residuum (higher Cryptogams
and some Animals).
(/) The leaving over of a central portion of cytoplasm, as a
non-nucleate blastophore, in the modified sperm morula,
where budding replaces true segmentation (Lumbricus,
Metazoa, &c).
(g) The differentiation of the basal cell of one of the earlier
stages of the fission of an attached sperm atogonium as a
nucleated blastophore (Helix and some Vertebrates ; it is
the first daughter-cell of the spermatogonium in Sponges).
(h) The abortion of some of the spermatogonial or oogonial
cells (Ascaris).
(i) The abortion of some of the gametes of a brood as
" polar bodies " in the Metazoa, owing to one appropriating
the greater part of the cytoplasm.
(A) The abortion of some of the gametonuclei, with or without
a minimal quantity of cytoplasm, as rejection-nuclei
(Ciliate Infusoria and some Fucacese).
. (I) The degradation of some of the oogametes or progametes
of a brood to serve as transmitting media for the spermatozoon
(canal-cells of Archegoniates and Gymnosperms).
(m) The retention of numerous gametonuclei in the peripheral
part of the apocytial cytoplasm, which is destined to
form an outer investment around a single central gamete
when transformed into the zygote (Peronosporese and
Ophryocystis?).
(n) The first formation of sterile cells in the pollen grain of
Gymnosperms, and of a vegetative nucleus in those of Angiosperms
representing the formation of a vegetative prothallus,
and having no real connection with the subsequent gametogenic
divisions of the other or sexual nucleus.
(o) The non-utilisation of some of the gametonuclei formed
in the pollen-tube of the Siphonogamous Metaphytes, and
the antheridium ofPeronospora. 1
1 This case finds a close parallel in the formation of the innumerable sper-