Translation from Von Hartmann 121 



the continuation of the species. The males always find 

 out the females of their own kind, but certainly not solely 

 through their resemblance to themselves. With many 

 animals, as, for example, parasitic crabs, the sexes so 

 little resemble one another that the male would be more 

 likely to seek a mate from the females of a thousand other 

 species than from his own. Certain butterflies are poly- 

 morphic, and not only do the males and females of the 

 same species differ, but the females present two distinct 

 forms, one of which as a general rule mimics the outward 

 appearance of a distant but highly valued species ; yet 

 the males will pair only with the females of their own 

 kind, and not with the strangers, though these may be 

 very likely much more Uke the males themselves. Among 

 the insect species of the strepsiptera, the female is a shape- 

 less worm which lives its whole life long in the hind body 

 of a wasp ; its head, which is of the shape of a lentil, pro- 

 trudes between two of the belly rings of the wasp, the 

 rest of the body being inside. The male, which only 

 lives for a few hours, and resembles a moth, nevertheless 

 recognises his mate in spite of these adverse circumstances, 

 and fecundates her. 



Before any experience of parturition, the knowledge 

 that it is approaching drives all mammals into solitude, 

 and bids them prepare a nest for their young in a hole or 

 in some other place of shelter. The bird builds her nest 

 as soon as she feels the eggs coming to maturity within 

 her. Snails, land-crabs, tree-frogs, and toads, all of them 

 ordinarily dwellers upon land, now betake themselves to 

 the water ; sea-tortoises go on shore, and many salt- 

 water fishes come up into the rivers in order to lay their 

 eggs where they can alone find the requisites for their 

 development. Insects lay their eggs in the most varied 

 kinds of situations, — in sand, on leaves, under the hides 

 and horny substances of other animals ; they often select 

 the spot where the larva will be able most readily to find 

 its future sustenance, as in autumn upon the trees that 



