Some Problems of Reproduction: a Comparative Study of ...
Some Problems of Reproduction: a Comparative Study of ...
Some Problems of Reproduction: a Comparative Study of ...
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
78 MABCUS M. HARTOG.<br />
heteroecism) in effecting rejuvenescence, and <strong>of</strong>ten replacing<br />
karyogamy: it is suggested that the evil effects <strong>of</strong> the prolonged<br />
association <strong>of</strong> cell and nucleus are due (a) to the<br />
nucleus responding less actively to the stimuli from the cytoplasm<br />
; (b) its consequently inadequate directive power; (c) to<br />
the resulting bad performance <strong>of</strong> its work by the cytoplast;<br />
(d) to the imperfect nutrition <strong>of</strong> the nucleus; (e) the failure<br />
<strong>of</strong> the cell as an organic whole.<br />
19. The process <strong>of</strong> nuclear reduction in progametal cells<br />
and gametes is, though general, neither uniform nor universal.<br />
Its occurrence in the pollen-mother-cells <strong>of</strong> Flowering Plants<br />
leads us to anticipate its occurrence in the mother-cells <strong>of</strong><br />
broods <strong>of</strong> reproductive cells generally, sexual or asexual.<br />
Pending the settlement <strong>of</strong> this point, explanation is premature.<br />
20. Replacement theories <strong>of</strong> fertilisation are inadmissible,<br />
since all fail to account for one or more <strong>of</strong> the following facts :<br />
(a) Multiple isogamy.<br />
(b) The non-discrimination <strong>of</strong> the broods <strong>of</strong> exo-isogametes<br />
into two categories, <strong>of</strong> which the members <strong>of</strong> either would pair<br />
with those <strong>of</strong> the other category, but not <strong>of</strong> their own.<br />
(c) The absence <strong>of</strong> " excretion phenomena " <strong>of</strong> any kind in<br />
so many cases <strong>of</strong> gametogeny.<br />
(d) The existence <strong>of</strong> true parthenogenesis <strong>of</strong> male as<br />
well as female gametes.<br />
(e) The formation <strong>of</strong> a male individual from the exclusively<br />
female oosphere <strong>of</strong> the Hive-bee.<br />
We have now finished our task; the theory (theses 1—17)<br />
and the hypothesis (18) set forth are based only on facts lying<br />
in the fields <strong>of</strong> biological observation and experiment; aa<br />
undertaking which should be more pr<strong>of</strong>itable than castlebuilding<br />
in the shadowy dreamland <strong>of</strong> & priori speculation.<br />
CORK, March 3,1891.'<br />
1<br />
Section VI, A was written after the completion <strong>of</strong> the rest <strong>of</strong> the MS.,<br />
and again modified during its passage through the press. Slight alterations<br />
and additions have been made at the same time in the rest <strong>of</strong> the study<br />
(July 30th, 1891).