413 



in severe winters, the stoat, or ermine as it is then called, assumes 

 a white dress, the white being more or less pure according to the 

 character of the season. 



In fact cases of mimicry, of one sort or another, occur throughout 

 the whole animal kingdom. Some of these resemblances may be 

 due to accident. In many instances, however, mimicry must afford 

 some protection to the mimicker against the attacks of its enemies, 

 thoiigh it may be questioned whether " natural selection " is 

 sufficient to account for its origin, and whether some other cause 

 must not be sought for and brought in fully to explain the 

 phenomenon. The whole subject needs further inquiry.* 



Below insects there are few classes among the Invertebrata which 

 call for particular consideration in this paper. The myriads of 

 forms inhabiting the sea do not form part of our subject. There 

 still remain, however, certain groups of invertebrate animals, found 

 either on land or in fresh water, which the local naturalist should 

 attend to, though the species are few compared with those of 

 insects, while their instincts and habits offer less variety to the 

 observer. The Entomostraca, Annelida, Entozoa, and MoUusca, 

 all open up to him an important field for investigation, in which 

 there is much yet to be done and learnt for the furtherance of 

 biological science. In reference to the Entomostraca, which abound 

 in our ponds and ditches, he will do well to read Sir J. Lubbock's 

 admirable memoir on the Daphnia (water-flea),t which is a model 

 for those who desire to take up the study of the structure and 

 habits of these aquatic animalculse. 



Fresh-waters indeed, no less than the sea, teem with life, and 

 deserve all the more consideration, as not merely having a fauna 

 of their own, consisting of species which never quit the water at 

 any period of their life, but as being the nurseiy of many other 

 species, mostly belonging to the class of insects, which are bom in 



* See "Wallace, p. 108, for some of the objections that have been made to 

 Mr. Bates' Theory of Mimicry. 



t Phil. Trans. 1857, p, 79. — See also another paper by bim " on some new 

 or little-known species of fresh-water entomostraca." Linn. Trans, vol. xxiv., 

 p. 197. Baird's work on the British Entomostraca, published by the Ray 

 Society, should also be consulted. 



