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 Manide and Orycteropide 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-Edwards, in discussing the inferences to be derived 
from the study of the foetal membranes of the Edentates', 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 communi- 
cation lead to a similar conclusion. 
2. On the Modification of a Race of Syrian Street-Dogs by 
means of Sexual Selection. By Dr. Van Dycx. With 
a Preliminary Notice by Cuartns Darwin, F.R.S., 
F.Z.S. 
[Received 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 
say that, after having carefully weighed to the best of my ability the 
various arguments which have been advanced against the principle of 
sexual selection, I remain firmly convinced of its truth. It is, how- 
ever, 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 Reichenau*, 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 me at all 
satisfactory. 
1 Annales des Sciences Naturelles, Zoolugie, 6me série, tome viii. p. 6 (1879). 
2 «Ueber den Ursprung der secundiren miinnlichen Geschlechtscharakteren 
&e.,” Kosmos, Jahrgang y. 1881, p. 172. 
Proc. Zoou. Soc.— 1882, No. XXV. 25 
