Page:The naturalist on the River Amazons 1863 v1.djvu/39

 It holds good in all families that the two sexes of the more brilliantly-coloured kinds are seldom equally beautiful; the females being often quite obscure in dress. There is a very large number of dull-coloured species in tropical countries. The tropics have also species in which the contrast between the sexes is greater than in any species of temperate zones; in some cases the males have been put in one genus and the females in another, so great is the difference between them. There are species of larger size, but at the same time there are others of smaller size in the same families in tropical than in temperate latitudes. If we reflect on all these facts, we must come to the conclusion, that climate, to which we are naturally at first sight inclined to attribute much, has little or no direct influence in the matter. Mr. Darwin was led to the same conclusion many years ago, when comparing the birds, plants, and insects of the Galapagos islands, situated under the equator, with those of Patagonia and Tropical America. The abundance of food, the high temperature, absence of seasons of extreme cold and dearth, and the variety of stations, all probably operate in favouring the existence of a greater number and variety of species in tropical than in temperate latitudes. This, perhaps, is all we can say with regard to the influence of climatal conditions. The causes which have produced the great beauty that astonishes us, if we really wish to investigate them, must be sought in other directions. I think that the facts above mentioned are calculated to guide us in the search. They show, for instance, that beauty of form and colour is