* Fritz Mller, ’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 Mller 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.

By comparing the structure of the leaves, their degree of complication, and their rudimentary parts in the six genera, we are led to infer that their common parent form partook of the characters of Drosophyllum, Roridula, and Byblis.  The leaves of this ancient form were almost certainly linear, perhaps divided, and bore on their upper and lower surfaces glands which had the power of secreting and absorbing.  Some of these glands were mounted on pedicels, and others were almost sessile; the latter secreting only when stimulated by the absorption of nitrogenous matter.  In Byblis the glands consist of a single layer of cells, supported on a unicellular pedicel; in Roridula they have a more complex structure, and are supported on pedicels formed of several rows of cells; in Drosophyllum they further include spiral cells, and the pedicels include a bundle of spiral vessels.  But in these three genera these organs do not possess any power of movement, and there is no reason to doubt that they are of the nature of hairs or trichomes.