[120] "Animals and Plants under Domestication," vol. ii. p. 189.

[121] "Origin of Species," 5th edition, 1839, p. 115.

[122] Ibid. p. 322.

[123] Ibid. p. 314.

[124] "Animals and Plants under Domestication," vol. ii. p. 104.

[125] _North British Review_, New Series, vol. vii., March 1867, p. 317.

[126] "Origin of Species," 5th edition, 1869, p. 212.

[127] See also the _Popular Science Review_ for July 1868.

[128] A bird with a keeled breast-bone, such as almost all existing birds possess.

[129] "Anatomy of Vertebrates," vol. iii. p. 792.

[130] Ibid. p. 793.

[131] As a tadpole is the _larval form_ of a frog.

[132] As Professor Huxley, with his characteristic candour, fully admitted in his lecture on the Dinosauria before referred to.

[133] "Transactions of the Geological Society of Glasgow," vol. iii.

[134] "Origin of Species," 5th edition, p. 354.

[135] See his address to the Geological Society, on February 19, 1869.

[136] See _Nature_, vol. i. p. 399, February 17, 1870.

[137] Ibid. vol. i. p. 454.

[138] "Habit and Intelligence," vol. i. p. 344.

[139] "Habit and Intelligence," vol. i. p. 345.

[140] "Origin of Species," 5th edition, p. 353.

[141] "Origin of Species," 5th edition, p. 381.

[142] "Origin of Species," 5th edition, 1869, p. 463.

[143] See his Catalogue of Acanthopterygian Fishes in the British Museum, vol. iii. p. 540.

[144] Proc. Zool. Soc. 1867, p. 102, and Ann. Mag. of Nat. Hist. vol. xx.

p. 110.

[145] See Catalogue, vol. iii. p. 469.

[146] Ibid. vol. v. p. 311.

[147] Ibid. p. 345.

[148] Ibid. p. 13.

[149] Ibid. p. 21.

[150] See Catalogue, vol. v. p. 24.

[151] Ibid. p. 52.

[152] Ibid. p. 109.

[153] Ibid. 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 h.o.m.ological 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 b.u.t.ton"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 woodp.e.c.k.e.r (_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 woodp.e.c.k.e.rs. 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.