[Illustration: Fig. 39.--Lipoptena of the stag.] The _Stratiome chameleon_ pays visits to flowers to seek for insects, on whose blood it feeds. Its very elongated larva lives in stagnant water. We have now to mention in the following passages parasites much less cruel in general, and which receive with greater delicacy the hospitality which is afforded them. We refer to some worms which pass, not their youth, but their mature age in the body of a neighbour, and use their host not as a _crèche_, but as a lying-in hospital. Their early youth is passed in freedom, but they soon give birth to a numerous progeny. The fate of the male is unknown; as to the female, she introduces herself in a microscopic state into the body of a neighbour, is developed there till she arrives at sexual maturity, and then quits her retreat to go and scatter her eggs. It appears, however, that these females are obliged to seek assistance from insects; but before they enter this living asylum, the male, which is not yet known, ensures by his fecundation the preservation of the species. We often find in summer in puddles of water, thin worms, which are 178 sometimes a foot long, resembling a violin string, and have for a long time puzzled naturalists. They are known by the name of _Gordius_, and have lately been very carefully studied, both with reference to their organization, to their mode of life, and their development. We give here the figure of a Gordius of the natural size. The _Mermis_, like the Gordius, passes its youth in the body of certain insects, and leaves its living cradle to scatter its eggs abroad. In this case, the embryos themselves go to seek for their host, and unlike the ichneumons, they use them with moderation. The life of the host is never compromised, and no functional disturbance is observed, notwithstanding the enormous size of the worm. [Illustration: Fig. 40.--Gordius aquaticus, natural size.] The Mermis is especially found after a heavy shower; some kinds of _Filaria_ are also more common when it rains. Under the title of "Notes on the Appearance of Worms after a Shower of Rain," I communicated to the Academy of Belgium some observations on these creatures, and these observations were recorded in the bulletins. Some years ago they brought me one morning, after a shower of rain, a quantity of worms, four or five inches in length, very thin, and 179 twisted round each other, which had been collected in the morning, on the flower borders of several gardens within the city. It was thought that there had been a shower of worms in the night. There was not one male worm among three hundred; all were full of eggs, and the young ones were already wriggling about within them.