Still, good mothers too may be found among fish, though far from frequently. One of the Guiana catfishes, known as Aspredo, very much resembles her countrywoman the Surinam toad in her nursery arrangements. Of course you know the Surinam toad—whom not to know argues yourself unknown—that curious creature that carries her eggs in little pits on her back, where the young hatch out and pass through their tadpole stage in a slimy fluid, emerging at last from the cells of this living honeycomb only when they have attained the full amphibian honours of four-legged maturity. Well, Aspredo among cat-fish manages her brood in much the same fashion; only she carries her eggs beneath her body instead of on her back like her amphibious rival. When spawning time approaches, and Aspredo's fancy lightly turns to thoughts of love, the lower side of her trunk begins to assume, by anticipation, a soft and spongy texture, honeycombed with pits, between which are arranged little spiky protuberances. After laying her eggs, the mother lies flat upon them on the river bottom, and presses them into the spongy skin, where they remain safely attached until they hatch out and begin to manage for themselves in life. It is curious that the only two creatures on earth which have hit out independently this original mode of providing for their offspring should both be citizens of Guiana, where the rivers and marshes must probably harbour some special danger to be thus avoided, not found in equal intensity in other fresh waters.
A prettily marked fish of the Indian Ocean, allied, though not very closely, to the pipe fishes, has also the distinction of handing over the young to the care of the mother instead of the father. Its name is Solenostoma (I regret that no more popular title exists), and it has a pouch, formed in this case by a pair of long broad fins, within which the eggs are attached by interlacing threads that push out from the body. Probably in this instance nutriment is actually provided through these threads for the use of the embryo, in which case we must regard the mechanism as very closely analogous indeed to that which obtains among mammals.
Some few fish, indeed, are truly viviparous; among them certain blennies and carps, in which the eggs hatch out entirely within the body of the mother. One of the most interesting of these divergent types is the common Californian and Mexican silver-fish, an inhabitant of the bays and inlets of sub-tropical America. Its chief peculiarity and title to fame lies in the extreme bigness of its young at birth. The full-grown fish runs to about ten inches in length, fisherman's scale, while the fry measure as much as three inches apiece; so that they lie, as Professor Seeley somewhat forcibly expresses it, 'packed in the body of the parent as close as herrings in a barrel.' This strange habit of retaining the eggs till after they have hatched out is not peculiar to fish among egg-laying animals, for the common little brown English lizard is similarly viviparous, though most of its relatives elsewhere deposit their eggs to be hatched by the heat of the sun in earth or sandbanks.
Mr. Hannibal Chollop, if I recollect aright, once shot an imprudent stranger for remarking in print that the ancient Athenians, that inferior race, had got ahead in their time of the modern Loco-foco ticket. But several kinds of fish have undoubtedly got ahead in this respect of the common reptilian ticket; for instead of leaving about their eggs anywhere on the loose to take care of themselves, they build a regular nest, like birds, and sit upon their eggs till the fry emerge from them. All the sticklebacks, for instance, are confirmed nest-builders: but here once more it is the male, not the female, who weaves the materials together and takes care of the eggs during their period of incubation. The receptacle itself is made of fibres of water-weeds or stalks of grass, and is open at both ends to let a current pass through. As soon as the lordly little polygamist has built it, he coaxes and allures his chosen mates into the entrance, one by one, to lay their eggs; and then when the nest is full, he mounts guard over them bravely, fanning them with his fins, and so keeping up a continual supply of oxygen which is necessary for the proper development of the embryo within. It takes a month's sitting before the young hatch out, and even after they appear, this excellent father (little Turk though he be, and savage warrior for the stocking of his harem) goes out attended by all his brood whenever he sallies forth for a morning constitutional in search of caddis-worms, which shows that there may be more good than we imagine, after all, in the domestic institutions even of people who don't agree with us.
The bullheads or miller's thumbs, those quaint big-headed beasts which divide with the sticklebacks the polite attentions of ingenious British youth, are also nest-builders, and the male fish are said to anxiously watch and protect their offspring during their undisciplined nonage. Equally domestic are the habits of those queer shapeless creatures, the marine lump-suckers, which fasten themselves on to rocks, like limpets, by their strange sucking disks, and defy all the efforts of enemy or fishermen to dislodge them by main force from their well-chosen position. The pretty little tropical walking-fish of the filuroid tribe—those fish out of water—carry the nest-making instinct a point further, for they go ashore boldly at the beginning of the rainy season in their native woods, and scoop out a hole in the beach as a place of safety, in which they make regular nests of leaves and other terrestrial materials to hold their eggs. Then father and mother take turns-about at looking after the hatching, and defend the spawn with great zeal and courage against all intruders.
I regret to say, however, there are other unprincipled fish which display their affection and care for their young in far more questionable and unpleasant manners. For instance, there is that uncanny creature that inserts its parasitic fry as a tiny egg inside the unsuspecting shells of mussels and cockles. Our fishermen are only too well acquainted, again, with one unpleasant marine lamprey, the hag or borer, so called because it lives parasitically upon other fishes, whose bodies it enters, and then slowly eats them up from within outward, till nothing at all is left of them but skin, scales, and skeleton. They are repulsive eel-shaped creatures, blind, soft, and slimy; their mouth consists of a hideous rasping sucker; and they pour out from the glands on their sides a copious mucus, which makes them as disagreeable to handle as they are unsightly to look at. Mackerel and cod are the hag's principal victims; but often the fisherman draws up a hag-eaten haddock on the end of his line, of which not a wrack remains but the hollow shell or bare outer simulacrum. As many as twenty of these disgusting parasites have sometimes been found within the body of a single cod-fish.
Yet see how carefully nature provides nevertheless for the due reproduction of even her most loathsome and revolting creations. The hag not only lays a small number of comparatively large and well-stored eggs, but also arranges for their success in life by supplying each with a bundle of threads at either end, every such thread terminating at last in a triple hook, like those with which we are so familiar in the case of adhesive fruits and seeds, like burrs or cleavers. By means of these barbed processes, the eggs attach themselves to living fishes; and the young borer, as soon as he emerges from his horny covering, makes his way at once into the body of his unconscious host, whom he proceeds by slow degrees to devour alive with relentless industry, from the intestines outward. This beautiful provision of nature enables the infant hag to start in life at once in very snug quarters upon a ready-made fish preserve. I understand, however, that cod-fish philosophers, actuated by purely personal and selfish conceptions of utility, refuse to admit the beauty or beneficence of this most satisfactory arrangement for the borer species.
Probably the best known of all fishes' eggs, however (with the solitary exception of the sturgeon's, commonly observed between brown bread and butter, under the name of caviare), are the queer leathery purse-shaped ova of the sharks, rays, skates, and dog-fishes. Everybody has picked them up on the seashore, where children know them as devil's purses and devil's wheelbarrows. Most of these queer eggs are oblong and quadrangular, with the four corners produced into a sort of handles or streamers, often ending in long tendrils, and useful for attaching them to corallines or seaweeds on the bed of the ocean. But it is worth noticing that in colour the egg-cases closely resemble the common wrack to which they are oftenest fastened; and as they wave up and down in the water with the dark mass around them, they must be almost indistinguishable from the wrack itself by the keenest-sighted of their enemies. This protective resemblance, coupled with the toughness and slipperiness of their leathery envelope or egg-shell, renders them almost perfectly secure from all evil-minded intruders. As a consequence, the dog-fish lay but very few eggs each season, and those few, large and well provided with nutriment for their spotted offspring. It is these purses, and those of the thornback and the edible skate, that we oftenest pick up on the English coast. The larger oceanic sharks are mostly viviparous.
In some few cases, indeed, among the shark and ray family, the mechanism for protection goes a step or two further than in these simple kinds. That well-known frequenter of Australian harbours, the Port Jackson shark, lays a pear-shaped egg, with a sort of spiral staircase of leathery ridges winding round it outside, Chinese pagoda wise, so that even if you bite it (I speak in the person of a predaceous fish) it eludes your teeth, and goes dodging off screw-fashion into the water beyond. There's no getting at this evasive body anywhere; when you think you have it, it wriggles away sideways, and refuses to give any hold for jaws or palate. In fact, a more slippery or guileful egg was never yet devised by nature's unconscious ingenuity. Then, again, the Antarctic chimæra (so called from its very unprepossessing personal appearance) relies rather upon pure deception than upon mechanical means for the security of its eggs. The shell or case in this instance is prolonged at the edge into a kind of broad wing on either side, so that it exactly resembles one of the large flat leaves of the Antarctic fucus in whose midst it lurks. It forms the high-water mark, I fancy, of protective resemblance amongst eggs, for not only is the margin leaf-like in shape, but it is even gracefully waved and fringed with floating hairs, as is the fashion with the expanded fronds of so many among the gigantic far-southern sea-weeds.
A most curious and interesting set of phenomena are those which often occur when a group of fishes, once marine, take by practice to inhabiting freshwater rivers; or, vice-versâ, when a freshwater kind, moved by an aspiration for more expansive surroundings, takes up its residence in the sea as a naturalised marine. Whenever such a change of address happens, it usually follows that the young fry cannot stand the conditions of the new home to which their ancestors were unaccustomed—we all know the ingrained conservatism of children—and so the parents are obliged once a year to undertake a pilgrimage to their original dwelling-place for the breeding season.