In other instances, the courses which lead from a similar starting-point
to a similar goal, separate widely in the middle of the development, as
in the Prawns with Nauplius-brood already described.
Finally, so that even the last possibility may be exhausted, it
sometimes happens that the greatest similarity occurs in the middle of
the development. The most striking example of this is furnished by the
Cirripedia and Rhizocephala, whether we compare the two orders or the
members of each with one another; from a segmentation quite different in
its course (see Figures 61 to 64) proceed different forms of Nauplius,
these become converted into exceedingly similar pupae, and from the
pupae again proceed sexually mature animals, differing from each other
toto coelo.
"If the formation of the organs occurs in the order corresponding to
their importance, this sequence must of itself be a criterion of their
comparative value in classification." THAT IS TO SAY, SUPPOSING THE
PHYSIOLOGICAL AND CLASSIFICATIONAL VALUE OF AN ORGAN TO COINCIDE! Just
as in Christian countries there is a catechismal morality, which every
one has upon his lips, but no one considers himself bound to follow, or
expects to see followed by anybody else, so also has Zoology its dogmas,
which are as universally acknowledged, as they are disregarded in
practice. Such a dogma as this is the supposition tacitly made by
Agassiz.
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