vol. vi. 208.

[154] Ibid. vol. viii. p. 507.

[155] Ibid. p. 509.

[156] Proc. Zool. Soc. 1868, p. 482

[157] "Origin of Species," 5th edition, 1869, p. 454.

[158] "Origin of Species," 5th edition, p. 459.

[159] See Ann. and Mag. of Nat. Hist., July 1870, p. 37.

[160] Professor Huxley's Lectures on the Elements of Comp. Anat. p. 184.

[161] For an enumeration of the more obvious homological relationships see
Ann. and Mag. of Nat. Hist. for August 1870, p. 118.

[162] See Ann. and Mag, of Nat. Hist., July 1870.

[163] Treatise on the Human Skeleton, 1858.

[164] Hunterian Lectures for 1864.

[165] Linnaean 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.

[174] Quoted by H. Stannius in his "Handbuch der Anatomie der
Wirbelthiere," Zweite Auflage, Erstes Buch, Sec. 7, p. 17.

[175] In his last Hunterian Course of Lectures, 1869.

[176] "The Science of Abnormal Forms."

[177] "Animals and Plants under Domestication," vol. ii. p. 322; and
"Origin of Species," 5th edition, 1869, p. 178.

[178] A remarkabl