394 THE DESCENT OF MAN. 



board and by the vibration of the intrinsic muscles of the 

 swim-bladder. By this latter means the Trigla produces 

 pure and long-drawn sounds which range over nearly an 

 octave. But the most interesting case for us is that of two 

 species of Ophidium, in which the males alone are provided 

 with a sound-producing apparatus, consisting of small mov- 

 able bones, with proper muscles, in connection with the 

 swim-bladder.* The drumming of the Umbrinas in the 

 European seas is said to be audible from a depth of twenty 

 fathoms; and the fisherman of Roclielle assert '^^that the 

 males alone make the noise during the spawning- time; and 

 that it is possible by imitating it to take them without 

 bait."f From this statement, and more especially from 

 the case of Ophidium, it is almost certain that in this, the 

 lowest class of the Vertebrata, as with so many insects and 

 spiders, sound-producing instruments have, at least in some 

 cases, been developed through sexual selection, as a means 

 for bringing the sexes together. 



AMPHIBIAKS. 



Urodela. I will begin with the tailed amphibians. The 

 sexes of salamanders or newts often differ much both in 

 color and structure. In some species prehensile claws 

 are developed on the fore legs of the males during 

 the breeding-season; and at this season in the male Triton 

 pahnipes the hind feet are provided with a swimming-web, 

 which is almost completely absorbed during the winter; so 

 that their feet then resemble those of the female. | This 

 structure no doubt aids the male in his eager search and 

 pursuit of the female. While courting her he rapidly 

 vibrates the end of his tail. With our common newts 

 {Triton punctatus and cristatus) a deep, much indented 

 crest is developed along the back and tail of the male 

 during the breeding-season, which disappears during the 



* " Comptes Rendus." Tom. xlvi, 1858, p. 353. Tom. xlvii, 1858, 

 p. 916. Tom. liv, 1863, p. 393. The noise made by the Umbrinas 

 (Scicena aquila), is said by some authors to be more like that of a 

 flute or organ, than drumming: Dr. Zouteveen, in the Dutch trans- 

 lation of this work (vol. ii, p. 36), gives some further particulars on 

 the sounds made by fishes. 



f The Rev. C. Kingsley, in " Nature," May, 1870, p. 40. 



^Bell "History of British Reptiles," 2nd edit. 1849, pp. 156-159. 



