392 THE DESCENT OF MAN. 



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 Geophagus act in the same manner; and in this genus, a 

 conspicuous protuberance becomes developed on the fore- 

 head of the males during the breeding- season. With the 

 various species of Chromids, 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 bright- 

 est species in their respective families; for instance, Hygro- 

 gonus 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 parents, has had 

 little or no influence on the differences in color between the 

 sexes. It is further manifest in all the cases in which the 

 males take exclusive charge of the nests and young, that 

 the destruction of the brighter-colored males would be far 

 more influential on the character of the race than the 

 destruction of the brighter-colored females; for the death 

 of the male during the period of incubation or nursing 

 would entail the death of the young, so that they could not 

 inherit his peculiarities; yet in many of -these very cases 

 the males are more conspicuously colored than the females. 

 In most of the Lophobranchii (Pipe-fish, Hippocampi, 

 etc.) the males have either marsupial sacks or hemispherical 

 depressions on the abdomen, in which the ova laid by the 

 female are hatched. The males also show great attachment 

 to their young.* The sexes do not commonly differ much 

 in color; but Dr. Giinther believes that the male Hippo- 

 campi are rather brighter than the females. The genus 

 Solenostoma, however, offers a curious exceptional case,f 

 for the female is much more vividly colored and spotted 



*YarrelV" Hist, of British Fishes," vol. ii, 1836, pp. 329, 338. 



f Dr. G Until er, since publishing an account of this species in " The 

 Fishes of Zanzibar," by Col. Playfair, 1866, p. 137, has re-examined 

 the specimens and has given me the above information. 



