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Show 2B SEXUAL SELECTION. !'AnT H. . 1 1 . 1 en into the ]arynx.43 are 11rovicled w1i 1 sacs w 11c l op · ) ·" th :For instance m. t 11 e ecl 'Ib l e f·orr (Rana esoulenta e I o :fill 1 " sacs are pec' uli. ar to t h e 1 l become when , ec rna es, anc ' 1 . bl d •· with al.l ' m. the net of ero.< L( ]'·- ·m ror , laro·o o·lobu ar a - b b d ,, ders <! :!tanding out one on each Sl' d 0 of the hca , near . ' f h tl , rrl·o croak of the male IS " the corners o t e mou l. ' . h f tl d. 1 e -ful. whilst t at o 1e thus render c1 exceo mg y pow ~ ' . 44 rrh vocal female is only a slight groanmg nOISe.. O r • urrrans differ considerably in st.ructure m tho S~\ mal b f tl fa111 genera o I'ly · and the1r development m all 1e ' . cases m ay be <a ttriLuted to sexual selcetwn. HErTILES. OheZonia.-Tortoises and turtles do not. offer wc1~murked sexual differences. In some species, the tml of tho male is longer than that of the female. J n som tl 10 pl as· ti·on or lower surface of the shel1l off th1e male' is slightly concave in relation to the bac.: o .t 1e f. 1 rrl1e male of the mud-turtle of tho Umtecl ema c. . f f t t . States (Ohrysemys pida) has claws on Its ront- oc WlCe as 1o no· . as tll OS e of' the female.' and these. are used Gw h1en b ·t 4~ ·ur1tho s xes um e. ·th the lnPP tortOJse of the a a- vv o ' . arros Islands (Testudo nigra) the males are ~ard to ~r;w to a larger size than the females: dnnng the bp tn· rm• g-sea on, ancl at no other time, tile male ntters a < < u.· hoarse bellowinrr noise, which can be heard nt the JS-tance 'of more ~ban a hunch·ed yatds; the female, on < • 4G the other hand, never uses her VOJCC'. . . 0?-ocodilia.-rr!Ie sexes apparently do not differ m 4:1 J. Bishop, in ''focl<l':; Cyclop. of Anat. nn<l Phys.' vol. iY. p. 1503. 44 Bell ibid. p. 112-1H. . , 18GD 553 . ,:; 1\tr. 'c J Mnynnrd 'Tho Americ~:tn Natural1~t, Doc. , P· · ..r. . . ' . . th Voy ''0 of tht! 4ti Sec mv 'J umnnl of Researches clurmg o 11 b " Beagle," ' lS-:1.5, p. 38·!. c;,,\1'. xrr. TIEPTILE~. 20 colonr; nor do I know that the males fight together, tbongh this is probable, for some kinds make a prodigious di:-;play before the females. Bartram 47 describes the lllale alligator us striving to win the female by spla hing and roaring in the midst of a lagoon," swollen " to an extent ready to burst, with his head and tail ': lif't cl up, he spins or t\\'irls round on the smface of " the water, like an Indian chief rchearsi11g his feats ·'of war." Dm·ing tho season of love, a musl'Y odonr is emitted by the snbmaxillttry glands or the erococ1ile, <.tnd pervades their haunts.48 Ophidia.-! have little to say about Snakes. Dr. Gunther informs me that the males are always smaller than the females, and generally have longer and slenderer tails; but he knows of no other difference in external structure. In regard to colour, Dr. Gunther can almost always distinguish the male from the female by his more strongly-pronounced tints; thus the blaek zig~ag band on the back of the male English viper is more distinctly defiued than in the femal<}. 'fhe difference is much plainer in the Rattle-snakes of N. America, the male of which, as the keeper in tho Zoological Gardens shewed me, can instantly Le distinguished from the female by having more lurid yellow about its whole body. In S. Africa the Buoepltalus capensis presents an analogous difference, for tho female " is never so fully "variegated with yellow on the sides, as the male.'' 49 The male of the Indian Dipsas cynoclon, on the other hand, is blackish-brown, with the belly partly black, whilst tlto female is reddish or yellowish-olive with the Lolly either uniform yellowish or marbled with black. 47 'Tmvels through Carolinn,' &c., 17Dl, p. 128 . 49 Owen, 'Anatomy of V or to brutes,' vol. i. 18GG, p. Gl5 . 4 • Sir Andrew Smith, 'Zoolog. of~. Africa: Roptilin,' 18.J.!J, 1•l. x. |