SEXUAL SELECTION' 4.49 



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, after depositing her eggs, were 

 immediately devoured by some enemy, for he is forced 

 incessantly to drive her from the nest." 



The males of certain other fishes inhabiting South 

 America and Ceylon, belonging to two distinct Orders, 

 have the extraordinary habit of hatching, within their 

 mouths or branchial cavities, the eggs laid by the females." 

 I am informed by Prof. Agassiz that the males of the Ama- 

 zonian species which follow this 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 Greophagus 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 Chromi(4g, as Prof. Agassiz 

 likewise informs me, sexual differences in color may be 

 observed, "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 in- 

 stance, Hygrogonous 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 protected or unprotected by the 



^ See Mr. Warington's most interesting description of the habits of tha 

 ffasterostews leiwus, in "Annals and Mag. of Nat. Hist.," November, 1855. 



88 Prof. Wyman, in "Proo. Boston Soc. of Nat. Hist.," Sept. 15, 1857. 

 Also Prof. Turner, in "Journal of Anatomy and Phys.," Nov. 1, 1866, p. 78. 

 Dr. Grunther has likewise described other cases. 



