12 SEXUAL SELECTION. Part IL 



male, which are absent in tlie female. These tentacles 

 are prolongations of the true skin, and therefore are not 

 homologous with the stiff hairs of the former species; but 

 it can hardly be doubted that both serve the same 

 purpose. AYhat this purpose may be it is difficult to 

 conjecture ; ornament does not here seem probable, but 

 we can hardly suppose that stiff hairs and flexible fila- 

 ments can be useful in anv ordinary wav to the males 

 alone. The Monacanthus scojoas, which was shewn to me 

 in the British Museum by Dr. Giinther, presents a nearly 

 analogous case. The male has a cluster of stiff, straisrht 

 spines, like those of a comb, on the sides of the tail ; and 

 these in a specimen six inches long were nearly an inch 

 and a half in length ; the female has on the same place 

 a cluster of bristles, which may be compared with those 

 of a tooth-brusli. In another species, the M. ^eronii, the 

 male has a brush like that possessed by the female of 

 the last species, whilst the sides of the tail in the female 

 are smooth. In some other species the same part of the 

 tail can be perceived to be a little roughened in the 

 male and perfectly sn^ooth in the female ; and lastly in 

 others, both sexes have smooth sides. In that stran2:e 

 monster, the Chimmra monstrosa, the male has a hook- 

 shaped bone on the top of the head, directed forwards, 

 with its ronnded end covered with sharp spines ; in the 

 female *' this crown is altogether absent," but what its 

 use may be is utterly unknown.^^ 



The structures as yet referred to are permanent in the 

 male after he has arrived at maturity ; but with some 

 Blennies and in another allied genus ^^ a crest is deve- 

 loped on the head of the male only during the breed- 



1" F. Buckland, in ' Land and Water,' July, 1868, p. 377, ^vith a 

 figure. 

 ^J8 Dr. Giinther, 'Catalogue of Tithes,' vol. iii. p. 221 and 240. 



