[33] For a fair and careful statement of the present balance of authoritative opinion upon the question, see H. F. Osborn, American Naturalist, 1892, pp. 537-67.
[34] [The above paragraph is allowed to remain exactly as Mr. Romanes left it. Chapters V and VI were however not completed. See [note] appended to Preface. C. Ll. M.
[35] See, especially, his excellent remarks on this point, Contemp. Rev. Sept. 1893.
[36] There is now an extensive literature within this region. The principal writers are Cope, Scott and Osborn. Unfortunately, however, the facts adduced are not crucial as test-cases between the rival theories—nearly all of them, in fact, being equally susceptible of explanation by either.
[37] For another and better illustration more recently published by Mr. Spencer, see The Inadequacy of Natural Selection, p. 22.
[38] Essays on Heredity, vol. i. p. 389.
[For further treatment of the subject under discussion see Weismann, The All-sufficiency of Natural Selection (Contemp. Rev. Sept. and Oct. 1893), and The Effect of External Influences upon Development. "Romanes Lecture" 1894, and Spencer, Weismannism once more (Cont. Rev. Oct. 1894). C. Ll. M.]
[39] Variation, &c., vol. ii. p. 206.
[40] E. g. Origin of Species, p. 178.
[41] Darwinism, p. 418.