242 
SEXUAL SELECTION: MAMMALS. 
PakT 1 
of the walrus the tusks are sometimes quite absent 
In the male elephant of India and in the male dugo**r 
the upper incisors form offensive weapons. In the 
narwhal one alone of the upper teeth is developed i J1 ^ 
the well-known, spirally-twisted, so called horn, which *' 
sometimes from nine to ten feet in length. It is belief 
that the males use these horns for finlitinn together; 1°' 
“ an unbroken one can rarely be got, and occasion"**- 
“ one may be found with the point of another jam 111 e 
“ into the broken place.” 6 The tooth on the opp° s * (t 
side of the head in the male consists of a rudiment abo* 1 
ten inches in length, which is embedded in the jaw- ^ 
is not, however, very uncommon to find double-hor" e ‘ 
male narwhals in which both teetli are well develop 6 *' 
In the females both teeth are rudimentary. The n 1 * 1 !j 
cachalot has a larger head than that of the female, ** D 
it no doubt aids these animals in their aquatic bat^ e “ 
Lastly, the adult male omithorhynchus is provided 
a remarkable apparatus, namely a spur on the fore-h^’ 
closely resembling the poison-fang of a venomous sn»b e ’ 
its use is not known, but we may suspect that it se?' 6 
as a weapon of offence. 7 It is represented by a 1110 ’ 
rudiment in the female. 
When the 
whi cl 
:b 
males are provided with weapons ■ . , 
the females do not possess, there can hardly be a do** 
that they are used for fighting with other males, aP 
that they have been acquired through sexual select* 011 
ON 
4 Mr. Lftmont (‘ Seasons with the Sea-Horses,’ 1361, J>- 1^-) ' 
that a good tusk ot the male walrus weighs I pounds, and * s * 01 ^,- t - 
than that of the female, which w< ighs about 3 pounds. The r»aI eS jj,, 
described as fighting ferociously. On the occasional absence °* ,,. 
tusks in the female, see Mr. It. Brown, -Proc. Zool, Soc.’ IS** 8 ’ P’ *' 
5 Owen, ‘Anatomy of Vertebrates,’ vol. iii. p. 283. 
8 Mr. R. Brown, in ‘ Proc. Zool. Soc.’ 1869, p. 553. 6 gg. 
’ Owen on the Cachalot and Omithorhynchus ib'd. vol. in- P‘ 
611. 
