) It is certain, however, that views essentially similar
are still to be met with everywhere in discussions on classification,
and that even within the last few years, the very sparingly successful
attempts to employ developmental history as the foundation of
classification have been repeated.
But how do these propositions agree with our observations on the
developmental history of the Crustacea? That these observations relate
for the most part to their "free metamorphosis" after their quitting the
egg, cannot prejudice their application to the propositions enunciated
especially with regard to "embryonal development" in the egg; for
Agassiz himself points out (paragraph 391) that both kinds of change are
of the same nature and of equal importance and that no "radical
distinction" is produced by the circumstance that the former take place
before and the latter after birth.
"The ovarian eggs of all animals are identical, small cells with
vitellus, germinal vesicle and germinal spot." Yes, somewhat as all
Insects are identical, small animals with head, thorax, and abdomen;
that is to say if, only noticing what is common to them, we leave out of
consideration the difference of their development, the presence or
absence and the multifarious structure of the vitelline membrane, the
varying composition of the vitellus, the different number and formation
of the germinal spots, etc.
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