[164] Hunterian Lectures for 1864.
[165] Linnæan Transactions, vol. xxv. p. 395, 1866.
[166] Hunterian Lectures for 1870, and Journal of Anat. for May 1870.
[167] See a Paper on the "Axial Skeleton of the Urodela," in Proc. Zool. Soc. 1870, p. 266.
[168] Just as Button's superfluous lament over the unfortunate organization of the sloth has been shown, by the increase of our knowledge, to have been uncalled for and absurd, so other supposed instances of non-adaptation will, no doubt, similarly disappear. Mr. Darwin, in his "Origin of Species," 5th edition, p. 220, speaks of a woodpecker (Colaptes campestris) as having an organization quite at variance with its habits, and as never climbing a tree, though possessed of the special arboreal structure of other woodpeckers. It now appears, however, from the observations of Mr. W. H. Hudson, C.M.Z.S., that its habits are in harmony with its structure. See Mr. Hudson's third letter to the Zoological Society, published in the Proceedings of that Society for March 24, 1870, p. 159.
[169] Dr. Cobbold has informed the Author that he has never observed a planaria divide spontaneously, and he is sceptical as to that process taking place at all. Dr. H. Charlton Bastian has also stated that, in spite of much observation, he has never seen the process in vorticella.
[170] Professor Huxley's Hunterian Lecture, March 16, 1868.
[171] Ibid. March 18.
[172] "Principles of Biology," vol. ii. p. 105.
[173] "Principles of Biology," vol. ii. p. 203.