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Show 1882.] DR. VAN DYCK ON SYRIAN STREET-DOGS. 367 of the alimentary organs, but in other respects, as their defensive armature, remarkably specialized. The two Old-World forms Manida and Orycteropida are so essentially distinct from all the American families, that it may even be considered doubtful whether they are derived from the same primary branch of mammals, or whether they may not be offsets from some other branch, the remaining members of which have been lost to knowledge. Alphonse Milne-Ed wards, in discussing the inferences to be derived from the study of the fcetal membranes of the Edentates1, has maintained that one of two views must be accepted :-either that it shows that no value can be attached to the placentation in seeking natural affinities; or that the Edentates as we know them now are not a homogeneous order, but should be separatedinto several distinct natural groups. It is the latter view to which he gives the preference. It need scarcely be remarked that the observations made in the present communication lead to a similar conclusion. 2. O n the Modification of a Kace of Syrian Street-Dogs by means of Sexual Selection. By Dr. V A N D Y C K . With a Preliminary Notice by C H A R L E S D A R W I N , F.R.S., F.Z.S. [Eeceived April 4, 1882.] Most of the naturalists who admit that natural selection has been effective in the formation of species, likewise admit that the weapons of male animals are the result of sexual selection-that is, of the best-armed males obtaining most females and transmitting their masculine superiority to their male offspring. But many naturalists doubt, or deny, that female animals ever exert any choice, so as to select certain males in preference to others. It would, however, be more correct to speak of the females as being excited or attracted in an especial degree by the appearance, voice, &c. of certain males, rather than of deliberately selecting them. I may perhaps be here permitted to sav that, after having carefully weighed to the best of m y ability the various arguments which have been advanced against the principle of sexual selection, I remain firmly convinced of its truth. It is, however, probable that I may have extended it too far, as, for instance, in the case of the strangely formed horns and mandibles of male Lamellicorn beetles, which have recently been discussed with much knowledge by W . von Reichenau2, and about which I have always felt some doubts. On the other hand, the explanation of the development of the horns offered by this entomologist does not seem to m e at all satisfactory. 1 Annales des Sciences Naturelles, Zoologie, 6me serie, tome viii. p. 6 (1879). 2 " Ueber den Ursprung der secundaren maunlichen Geschlechtscharakteren &c," Kosmos, Jahrgang v. 1881, p. 172. PROC. ZOOL. Soc-1882, No. XXV. 25 |
