Ocypoda

The orifice opens into the branchial cavity behind a conical lobe, which stands above the third foot in place of a branchia which is wanting in Ocypoda.

Facts and Arguments for Darwin Fritz Muller 1859

Whilst in Grapsus the water is allowed to reach the branchiae only from the front, I saw it in Ocypoda flow in also through the orifice just described.

Facts and Arguments for Darwin Fritz Muller 1859

The swift-footed Sand-Crabs (Ocypoda) are exclusively terrestrial animals, and can scarcely live for a single day in water; in a much shorter period a state of complete relaxation occurs and all voluntary movements cease.

Facts and Arguments for Darwin Fritz Muller 1859

In the position of posterior entrant orifice and the accompanying peculiarities of the third and fourth pairs of feet, two other non-aquatic species of the same family, which I have had the opportunity of examining, agree with Ocypoda.

Facts and Arguments for Darwin Fritz Muller 1859

The other, a smaller Gelasimus, not described in Milne-Edwards '' Natural History of Crustacea, 'which prefers drier places and is not afraid to run about on the burning sand under the vertical rays of the noonday sun in December, but can also endure being in water at least for several weeks, resembles Ocypoda in having these brushes composed of non-setiform, delicate hairs, indeed even more delicate and more regularly constructed than in Ocypoda.

Facts and Arguments for Darwin Fritz Muller 1859

In the case before us it is 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.

Facts and Arguments for Darwin Fritz Muller 1859

Nevertheless it may be remarked that in both species, especially in Ocypoda, the olfactory filaments in their ordinary situation are very much reduced, and when they are in the water their flagella never perform the peculiar beating movements which may be observed in other Crabs, and even in the larger Gelasimus; moreover, the organ of smell must probably be sought in these air-breathing Crabs, as in the air-breathing Vertebrata, at the entrance to the respiratory cavity.

Facts and Arguments for Darwin Fritz Muller 1859

From this point of view we might certainly say that a widely gaping fissure which had nothing prejudicial in it to Aratus Pisonii among the foliage of the mangrove bushes, was not suitable to the Ocypoda living in sand; that in the latter, in order to prevent the penetration of the sand, the orifice of the branchial cavity must be placed at its lowest part, directed downwards, and concealed between broad surfaces fringed with protective brushes of hair.

Facts and Arguments for Darwin Fritz Muller 1859

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.

Facts and Arguments for Darwin Fritz Muller 1859

I therefore put into the same water from which I had just taken an unconscious Ocypoda, with its legs hanging loosely down, a specimen of Lupea diacantha which had been reduced to the same state by being kept in the air, and this recovered in the water just as the Ocypoda did in the air.)

Facts and Arguments for Darwin Fritz Muller 1859