preservation of such intermediate forms being only exceptional, this
last mentioned circumstance will not be regarded as of very great
significance by any one who has traced the development of an animal upon
larvae fished from the sea, and had to seek in vain for months, and even
years, for those transitional forms, which he nevertheless knew to be
swarming around him in thousands.

A few examples may show how contradictions might come forth as necessary
results of the Darwinian hypotheses.

It seems to be a necessity for all crabs which remain for a long time
out of the water (but why is of no consequence to us here), that air
shall penetrate from behind into the branchial cavity. Now these crabs,
which have become more or less estranged from the water, belong to the
most different families--the Raninidae (Ranina), Eriphinae (Eriphia
gonagra), Grapsoidae (Aratus, Sesarma, etc.), Ocypodidae (Gelasimus,
Ocypoda), etc., and the separation of these families must doubtless be
referred to a much earlier period than the habit of leaving the water
displayed by some of their members. The arrangements connected with
aerial respiration, therefore, could not be inherited from a common
ancestor, and could scarcely be accordant in their construction. If
there were any such accordance not referable to accidental resemblance
among them, it would have to be laid in the scale as evidence against
the correctness of Darwin's views. I shall show hereafter how in this
case the result, far from presenting such contradictions, was rather in
the most complete harmony with what might be predicted from Darwin's
theory.

(FIGURE 1. Melita exilii n. sp., male, enlarged five times. The large
branchial lamellae are seen projecting between the legs.)