The Romance of Natural History, Second Series

by Philip Henry Gosse

There is a large species of Crab (Dromia) found in the West Indies, which is invariably found covered with a dense mass of sponge. The sponge is found to have grown in such a manner as to fit every prominence and cavity of the crab, exactly as if a plastic material had been moulded on it, yet it is not adherent to it, but is merely held in position by the hindmost pair of feet, which in this genus of crabs, are turned upwards, and apparently serve no other purpose than that of hooks to hold on the sponge in situ.

On our own shores we are familiar with the Hermit crabs making use of various kinds of univalve shells as houses to protect their softer hindparts; but in many of these cases there is a third party in the transaction, which is made to work for the crab's especial advantage. The shell of the mollusk is sometimes covered with a sort of fleshy polype-mass (Hydractinia echinata), which is parasitic on the shell. The shell, however, being tenanted also by the active crab, the polype, as it grows, moulds itself on the crab's body, and thus extends the dimensions of its house, so that it has no necessity either to enlarge its dwelling by the absorption of part of the interior shell-wall, or to leave this shell and search for one of ampler size, as other Hermit-crabs are obliged to do who have not the advantage of so accommodating a fellow-lodger. "One can understand," says Dr Gray, "that the Crab may have the instinct to search for shells, on which the coral [polype] has begun to grow; but this will scarcely explain why we never find the [polype] except on shells in which Hermit-crabs have taken up their residence."[233]

Small Annelids and Crustaceans not unfrequently burrow into the stony walls of corals; but Dr Gray records a much more uncommon case, from the Guilding collection. "It is an expanded coral, which forms a thin surface on the top of another coral, and is furnished with a number of small, depressed, horizontal cases, opening with an oblong mouth. Some of these contain within them a small, free, crustaceous animal, a Cymothoa, which nearly fits the case; and it is evident that, by their moving backwards and forwards on the surface, they have caused the animal of the coral to form one of these cases for the protection of each specimen."[234]

The manner in which this result is obtained is thus explained—"The animals which form their habitation in corals, appear to begin their domicile in the same way as the barnacles before referred to; they take advantage of the soft and yielding nature of the animals which form the corals, &c., and taking up a lodgement in their body, all they have to do is to keep a clear passage in it, either by the moving backwards and forwards, the exertion of their limbs, or the ingress or egress of water to and from their bodies, and in time, as the coral is secreted by the animal, it will form a wall round them; but if, by any accident, the parasite animal should not keep a passage from the coral to the surface of the body of the animal clear, which it must be constantly induced to do, since by this means it procures food, the coral animal will in a very short time close over it and bury it alive in the mass of the coral; and this, from the number of these animals, of all sizes and in different stages of growth, which are to be found in the substance of the large and massive corals, must often be occurring. Thus the Italian romance is often literally fulfilled in nature."

Certain birds are parasitic, in this sense, that they compel or induce other birds to perform the labour of incubation and of rearing their young. The Rhea or Ostrich of South America is parasitical on its own species; the females laying each several eggs in the nests of several other females, and the male ostrich taking all the cares of incubation. More familiar examples, however, occur in our own Cuckoo, and in the Cowpen birds (Molothrus pecoris and M. niger) of North and South America. "These fasten themselves," as has been remarked by Mr Swainson, "on another living animal, whose animal heat brings their young into life, whose food they live upon, and whose death would cause theirs during the period of infancy."

The habit, at least in the case of the European Cuckoo, is so well known, that I need not do more than merely allude to the fact, that the female seeks for the nests of other insect-eating birds, always much smaller than itself, and deposits its own eggs,—a single egg in each; that this stranger egg is hatched by the foster-mother with all care, and the young bird is nurtured with all tenderness even at the expense of its own proper eggs and young, which in general are sacrificed in the course of the process. Every schoolboy knows these facts, but few perhaps have ever suspected the existence of a romantic feeling of love and fealty in the little bird towards the cuckoo herself, prompting the rendering of the service required as a coveted honour. Yet a naturalist has communicated to Mr Yarrell some facts which certainly look this way; and because they are indubitably the very romance of natural history, I cite them, leaving my readers to judge of their value.

"As you have contributed," writes Mr W. C. Newby of Stockton, "so much to the information and amusement of the numerous class of readers who take an interest in subjects of natural history, I consider it my duty to communicate first to you, what appears to me a new fact in the habits and character of that general favourite the cuckoo.

"An egg of this bird was brought to me on the 6th instant, which had been taken from the nest of the yellow bunting, at a short distance from this town, and the boy who got the egg gave the following account, which, I think, may be relied on. When bird-nesting the previous Saturday, he found a nest of the gold spink (a local name for the yellow bunting) with the young birds just hatched. On visiting the nest the following day, he flushed the old bird, having seen her sitting on it, but the young birds were all excluded, and were lying dead near; and to his surprise, a single egg—the one he brought to me—occupied the place of the callow brood. He took away the egg (which is now in my possession) so that it is impossible to corroborate the statement in any degree. The above circumstance was first named to me by Tom Green, a well-known character and naturalist in this town, whom I have always found to be accurate in his observations on birds, and by him I was referred to the boy. On my objecting to Green that the accident appeared incredible, because unnatural, and contrary to strong parental instinct, he replied, "Ay, sir, but little birds are mightily ta'en up with a cuckoo; they'll awmost dee out for them;" and he related the following fact which came under his own observation. When out with his gun, collecting birds to stuff, (animal-preserving being one of his many trades), he shot at and wounded a cuckoo, which, after flying some distance, fell upon a hedge with its wings outstretched: the attendant bird, which in this case was one of the pipits, continued in the flight of its patron after the shot, and when Green approached, he found it sitting on the body of the dead cuckoo.[235]

"It has been supposed by some, that small birds follow the cuckoo for the sake of annoyance, mistaking it for a sparrow-hawk, to give public notice of a pirate abroad, and to warn all peaceful subjects of the air against a common danger. But this is clearly not so, for the flight and cries clearly distinguish the feelings in the two cases. The attendance on the cuckoo is at a distance, silent and respectful; but in the other we have a sort of hue and cry raised, as it were, against a felon, and which is kept up from place to place, if not to the shame, at least to the discomfiture of the culprit.