sufficient to refer to the Gelasimus of the mangrove swamps, which
shares the same conditions of life with various Grapsoidae and yet does
not agree with them, but with the arenicolous Ocypoda.


CHAPTER 6. STRUCTURE OF THE HEART IN THE EDRIOPHTHALMA.

Scarcely less striking than the example of the air-breathing Crabs, is
the behaviour of the heart in the great section Edriophthalma, which may
advantageously be divided, after the example of Dana and Spence Bate,
only into two orders, the Amphipoda and the Isopoda.

In the Amphipoda, to which the above-mentioned naturalists correctly
refer the Caprellidae and Cyamidae (Latreille's Laemodipoda), the heart
has always the same position; it extends in the form of a long tube
through the six segments following the head, and has three pairs of
fissures, furnished with valves, for the entrance of the blood, situated
in the second, third, and fourth of these segments. It was found to be
of this structure by La Valette in Niphargus (Gammarus puteanus), and by
Claus in Phronima; and I have found it to be the same in a considerable
number of species belonging to the most different families.* (* The
young animals in the egg, a little before their exclusion, are usually
particularly convenient for the observation of the fissures in the
heart; they are generally sufficiently transparent, the movements of the
heart are less violent than at a later period, and they lie still even
without the pressure of a glass cover. Considering the common opinion as
to the distribution of the Amphipoda, namely, that they increase in
multiplicity towards the poles, and diminish towards the equator, it may
seem strange that I speak of a considerable number of species on a
subtropical coast. I therefore remark that in a few months and without