Chap. XII. Fishes. 345 



sexes of the bright coloured Crenilabrus massa and mdcps work 

 together in building their nests with sea-weed, shells, &c. 35 

 But the males of certain fishes do all the work, and afterwards 

 take exclusive charge of the young. This is the case with the dull- 

 coloured gobies, 36 in which the sexes are not known to differ in 

 colour, and likewise with the sticklebacks (Gasterosteus), in which 

 the males become brilliantly coloured during the spawning season. 

 The male of the smooth-tailed stickleback (G. leiurus) performs 

 the duties of a nurse with exemplary care and vigilance during 

 a long time, and is continually employed in gently leading back 

 the young to the nest, when they stray too far. He courageously 

 drives away all enemies, including the females of his own species 

 It would indeed be no small relief to the male, if the female, aftei 

 depositing her eggs, were immediately devoured by some enemy 

 for he is forced incessantly to drive her from the nest. 37 



The males of certain other fishes inhabiting South Americj 

 and Ceylon, belonging to two distinct Orders, have the extra 

 ordinary habit of hatching within their mouths or branchial 

 cavities, the eggs laid by the females. 38 I am informed by 

 Professor Agassiz that the males of the Amazonian species 

 which follow tins habit, " not only are generally brighter than 

 " the females, but the difference is greater at the spawning-season 

 " than at any other time." The species of Geophagus act in the 

 same manner ; and in this genus, a conspicuous protuberance 

 becomes developed on the forehead of the males during the 

 breeding-season. With the various species of Chromids, as 

 Professor Agassiz likewise informs me, sexual differences in 

 colour may be observed, u whether they lay their eggs in the 

 " water among aquatic plants, or deposit them in holes, leaving 

 " them to come out without further care, or build shallow nests 

 " in the river mud, over which they sit, as our Pomotis does. 

 " It ought also to be observed that these sitters are among the 

 " brightest species in their respective families ; for instance, 

 " Hygrogonus is bright green, with large black ocelli, encircled 

 " with the most brilliant red." Whether with all the species of 

 Chromids it is the male alone which sits on the eggs is not 

 known. It is, however, manifest that the fact of the eggs being 



35 According to the observations nals and Mag. of Nat. Hist.' Novera- 

 of M. Gerbe ; see Giinther's ' Record ber 1855. 



•>f Zoolog. Literature,' 1865, p. 38 Prof. Wyman, in ' Proc. Boston 



19+. Soc. of Nat. Hist.' Sept. 15, 1857. 



36 Cuvier, ' Regne Animal,' vol. Also Prof. Turner, in ' Journal of 

 n. 1829, p. 242. Anatomy and Phys.' Nov. 1, 1866, 



87 See Mr. Waringtou's most p. 78. Dr. Gunther has likewise 

 interesting description of the habits described other cases, 

 of the Gasterosteus leiurus, in ' An- 



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