OCR Text |
Show 2-.1: SEXUAL SELECTION. l'AltT II. AMPIIIBIANS. U1·oaelce.-First for the tailed amphibians. Tho sex s of salamanders or newts often dtff?r much bo.th in. colour and structure. In some speciC~ prehensile elaws are developed on the fore-legs o~ tho mal~s durino- tho breeding-season; :mel at thls scaso~ m the l~alo Tt·iton paZ.mipes the h~nd-feet are provHled wi~h a swimming web, which IS almost. completely absorbc:l dnriJJg the winter ; so that thou feet then Fig. 31. Triton cristnlus (half nnlurnl siz~, from Bell's 'Brllibh H~pliles '). U pprr t\gurc, mnle during the breculng-scnsou; lower figure, female. resemble those of the fcmalo. 38 This structure no doubt aids the malo in his eager scareh and pursuit of the female. With our common newts (Triton punctatus and cristatus) a deep, much-indented crest is developed alo11g the bac:k and tail of the male during the bree~ino ·-season, being absorbed during the winter. It IS no~ furni!:lbed, as Mr. St. George l\fivart informs me, a~ D~ll, 'History of Driiislt Reptiles,' 2nd edit. 18·19, p. 15G-15D. C':u1•. XII. AMPIIIJ3IAN, ', 25 with muscles, and therefore cannot be used for locomotion. As during the season of courtship it becomes cclgcc1 'tvith bright colours, it serves, there can hardly be a doubt, as a masculine ornament. In many species tho body presents strongly contrasted, though l~rid tints; and these become more vivid during tho breeding-season. The male, for in tnnce, of our common little newt (Triton p~mctat~ts) is "brownish-grey "·above, passing into yellow b neath, which" in the "spring becomes a ri<·h bright orange, marked every" where with round clark spots." The edge of the crest also is then tipped with bright red or violet. The female is usually of a yellowish-brown colour with scattered brown U.ots; and the lower surface is often quite plairi.39 The young are obscurely tinted. The ova arc fertilised during the act of deposition and. are not sub$equently tended by either parent. vVe may therefore conclude that the males acquired their strongly-marked colours and ornamental appendages through sexual selection; these being transmitted. either to the rnale o:ff..,pring alone or to both sexes. An~wa or Bat?·achia.-'With many frogs and toads the colours evidently serve as a protection, such as the bright green tints of tree-frogs and the obscure mottled shades of many terrestrial species. The mo. t conspieuously coloured toad whith I ever saw, namely the Phryniscus n£gricans,40 had the whole upper surface of the body as black as ink, with the soles of the feet and parts of the abdomen spotted with the brightest vermilion. It crawled about the bare sandy or open grassy plains of La Plata under a scorching sun, and 30 13 •11, ibid. p. HG, 151. ~0 'Zoology of the Vuyage of the ".Beagle,"' 18!3. "Reptiles," l•y l\11'. Bell, p. 1D. |