The bat of the high mountains of Bavaria, known under the name of Vespertilio mystacinus, harbours a nematode, the Rictularia plagiostoma, the same which is found in Egypt in the hedgehog (Erinaceus auritus). The bat on the banks of the Rhine has not this remarkable worm. We must therefore conclude that the bat of Bavaria finds and eats the same insect as the hedgehog in Egypt, and that this insect does not live on the banks of the Rhine. We have never met with this nematode in the mystacines of Belgium, and yet we have opened them by hundreds.
A bird found in Florida, the Anhinga, has in its brain a nematode whose presence in that organ is not accidental.
The Echinorhynchi form a very remarkable group of parasites. They migrate from one host to another; but the vehicle by which the greater part of them is conveyed is not known. We represent in [Fig. 72] a species which is very common in the intestine of the sprat.
It is known that these worms migrate when young, and undergo metamorphoses when they change their host. The Asellus aquaticus of fresh water, harbours besides other worms, the Echinorhynchus hœruca; the Gammarus pulex, another fresh-water crustacean, lodges the larva of the Echinorhynchus proteus ([Fig. 72]). We commonly find this beautiful species of the Echinorhynchus
in the alimentary cavity of the sprat, and it is easily distinguished by its peculiar form and its orange colour.
Fig. 72.—Echinorhynchus proteus of the Sprat.
