fully represented in No. 7, is formed by a loose fold of skin arising from either side of the creature.  In the illustration this fold is partly withdrawn, so as to show the young pipe-fish within their safe retreat after hatching out.  It is said, I know not how truly, that the young fry will stroll out for an occasional swim on their own account, but will return at any threat of danger to their father’s bosom, for a considerable time after the first hatching.  This is just like what one knows of kangaroos and many other pouched mammals, where the mother’s pouch becomes a sort of nursery, or place of refuge, to which the little ones return for warmth or safety after every excursion.

[Illustration:  NO. 7.  POUCH OF PIPE-FISH.]

The sea-horses and many other fish have similar pouches; but, oddly enough, in every case it is the male fish which bears it, and which undertakes the arduous duty of nurse for his infant offspring.

A few female fish, on the other hand, even hatch the eggs within their own bodies, and so apparently bring forth their young alive, like the English lizard among reptiles.  This, however, is far from a common case:  indeed, in an immense number of instances, neither parent pays the slightest attention to the eggs after they are once laid and got rid of:  the spawn is left to lie on the bottom and be eaten or spared as chance directs, while the young fry have to take care of themselves, without the aid of parental advice and education.  But exceptions occur where both parents show signs of realizing the responsibilities of their position.  In some little South American river fish, for instance, the father and mother together build a nest of dead leaves for the spawn, and watch over it in unison until the young are hatched.  This case is exactly analogous to that of the doves among birds:  I may add that wherever such instances occur they always seem to be accompanied by a markedly gentle and affectionate nature.  Brilliantly-coloured fighting polygamous fishes are fierce and cruel:  monogamous and faithful animals are seldom bright-hued, but they mate for life and are usually remarkable for their domestic felicity.  The doves and love-birds are familiar instances.

Frogs are very closely allied to fish:  indeed, one may almost say that every frog begins life as a fish, limbless, gill-bearing, and aquatic, and ends it as something very like a reptile, four-legged, lung-bearing, and more or less terrestrial.  For the tadpole is practically in all essentials a fish.  It is not odd, therefore, to find that certain frogs reproduce, in a very marked manner, the fatherly traits of their fish-like ancestors.  There is a common kind of frog in France, Belgium, and Switzerland, which does not extend to England, but which closely recalls the habits of the stickleback and the pipe-fish.  Among these eminently moral amphibians, it is the father, not the mother, who takes entire charge of the family.  The female lays her spawn in the