The Descent of Man

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. (37. See Mr. Warington's
most interesting description of the habits
of the Gasterosteus leiurus in 'Annals and Magazine
of Nat. History,' November 1855.)
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. (38. Prof.
Wyman, in 'Proc. Boston Soc. of Nat. Hist.'
Sept. 15, 1857. Also Prof. Turner, in 'Journal of
Anatomy and Physiology,' Nov. 1, 1866, p. 78.
Dr. Gunther has likewise described other cases.)
I am informed by Professor Agassiz that
the males of the Amazonian species which follow
this habit, "not only are generally brighter
than the females, but the difference is greater at