"Are there any other kinds of fish," asked Willy, "that make nests and take care of their young ones like the three species of sticklebacks?" Yes, there are several kinds of fish which do so, but no other British fresh-water kinds, I believe. There is the salt-water _Lumpsucker_, a fish of strange form and brilliant colour--you know the pickled specimen in my study--whose young soon after birth fix themselves to the sides and on the back of their male parent, who sails, thus loaded, away to deeper and more safe retreats. There are the long pipe-fishes, the males of which possess each a singular pouch on the tail; in this the eggs of the female are deposited and matured; the young ones occasionally leave their strange abode, and after swimming about for a time return to it again, reminding us in this respect of the kangaroos and opossums amongst mammalia. There are also fish which inhabit the rivers of Demerara which make nests and show great attachment to their young ones, and I dare say several other fish will be found to do the same. [Illustration: SNAIL LEECH.] "Oh! papa, do look here; as I was turning over this bit of flat tile I saw in the water I found a creature something like a leech, and on raising it up I saw what looks like a quantity of the animal's eggs, and she seems to be sitting upon them as a hen upon her eggs." All right, Jack; let me look, I dare say it is one of the snail-leeches. Yes, to be sure it is, and here are the eggs which the creature carefully covers with her body, and upon which she will sit till the young ones are formed; the small brood, sometimes one hundred and fifty or more in number, then attach themselves to the under surface of the parent, and are carried about wherever she goes. There are various species of this interesting family; all are inhabitants of fresh water; some incubate or sit upon their eggs, others carry them about in a hollow formed by the contraction of the sides. They have a long tubular proboscis, by means of which they suck out the juices of pond-snails and other water creatures. These snail-leeches move along in the same way as the common horse-leech and the medicinal leech, namely, by fixing the head-part on to the surface of some substance in the water and then drawing the hinder part up to it; they then extend the head-portion and fix it upon another spot, again drawing up the other extremity. But the leeches, properly so called, have all red blood; that of the snail-leeches is colourless.