* Fritz Müller, ‘Facts for Darwin,’ Eng. trans. 1869, p. 139. The rhizocephalous crustaceans are allied to the cirripedes. It is hardly possible to imagine a greater difference than that between an animal with prehensile limbs, a well-constructed mouth and alimentary canal, and one destitute of all these organs and feeding by absorption through branching root-like processes. If one rare cirripede, the Anelasma squalicola, had become extinct, it would have been very difficult to conjecture how so enormous a change could have been gradually effected. But, as Fritz Müller remarks, we have in Anelasma an animal in an almost exactly intermediate condition, for it has root-like processes embedded in the skin of the shark on which it is parasitic, and its prehensile cirri and mouth (as described in my monograph on the Lepadidae, ‘Ray Soc.’ 1851, p. 169) are in a most feeble and almost rudimentary condition. Dr. R. Kossmann has given a very interesting discussion on this subject in his ‘Suctoria and Lepadidae,’ 1873. See also, Dr. Dohrn, ‘Der Ursprung der Wirbelthiere,’ 1875, p. 77. ** Bentham and Hooker, ‘Genera Plantarum.’ Australia is the metropolis of the genus, forty-one species having been described from this country, as Prof. Oliver informs me. [page 358] hear from Prof. Oliver) two species; the former confined to the western parts of the Cape of Good Hope, and the latter to Australia. It is a strange fact that Dionaea, which is one of the most beautifully adapted plants in the vegetable kingdom, should apparently be on the high-road to extinction. This is all the more strange as the organs of Dionaea are more highly differentiated than those of Drosera; its filaments serve exclusively as organs of touch, the lobes for capturing insects, and the glands, when excited, for secretion as well as for absorption; whereas with Drosera the glands serve all these purposes, and secrete without being excited.