movement makes up for the loss of viscid secretion.  In every case it is some part of the leaf which moves.  In Aldrovanda it appears to be the basal parts alone which contract and carry with them the broad, thin margins of the lobes.  In Dionaea the whole lobe, with the exception of the marginal prolongations or spikes, curves inwards, though the chief seat of movement is near the midrib.  In Drosera the chief seat is in the lower part of the tentacles, which, homologically, may be considered as prolongations of the leaf; but the whole blade often curls inwards, converting the leaf into a temporary stomach.

There can hardly be a doubt that all the plants belonging to these six genera have the power of dissolving animal matter by the aid of their secretion, which contains an acid, together with a ferment almost identical in nature with pepsin; and that they afterwards absorb the matter thus digested.  This is certainly the case with Drosera, Drosophyllum, and Dionaea; almost certainly with Aldrovanda; and, from analogy, very probable with Roridula and Byblis.  We can thus understand how it is that the three first-named genera are provided with such small roots, and that Aldrovanda is quite rootless; about the roots of the two other genera nothing is known.  It is, no doubt, a surprising fact that a whole group of plants (and, as we shall presently see, some other plants not allied to the Droseraceae) should subsist partly by digesting animal matter, and partly by decomposing carbonic acid, instead of exclusively by this latter means, together with the absorption of matter from the soil by the aid of roots.  We have, however, an equally anomalous case in the animal kingdom; the rhizocephalous crustaceans do not feed like other animals by their mouths, for they are destitute of an [page 357] alimentary canal; but they live by absorbing through root-like processes the juices of the animals on which they are parasitic.*

Of the six genera, Drosera has been incomparably the most successful in the battle for life; and a large part of its success may be attributed to its manner of catching insects.  It is a dominant form, for it is believed to include about 100 species, which range in the Old World from the Arctic regions to Southern India, to the Cape of Good Hope, Madagascar, and Australia; and in the New World from Canada to Tierra del Fuego.  In this respect it presents a marked contrast with the five other genera, which appear to be failing groups.  Dionaea includes only a single species, which is confined to one district in Carolina.  The three varieties or closely allied species of Aldrovanda, like so many water-plants, have a wide range from Central Europe to Bengal and Australia.  Drosophyllum includes only one species, limited to Portugal and Morocco.  Roridula and Byblis each have (as I