ILLUSTRATIVE OF NATURAL SELECTION. 155 



many analogous cases occur ; and as the whole 

 history of many of these has been investigated by 

 breeding successive generations from the egg, it is 

 to be hoped that some of our British Lepidopterists 

 will give us a connected account of all the abnormal 

 phenomena which they present. Among the Coleop- 

 tera Mr. Pascoe has pointed out the existence of two 

 forms of the male sex in seven species of the two 

 genera Xenocerus and Mecocerus belonging to the 

 family Anthribidae, (Proc. Ent. Soc. Lond., 1862); 

 and no less than six European Water-beetles, of the 

 genus Dytiscus, have females of two forms, the most 

 common having the elytra deeply sulcate, the rarer 

 smooth as in the males. The three, and sometimes 

 four or more, forms under which many Hymenop- 

 cerous insects (especially Ants) occur, must be con- 

 sidered as a related phenomenon, though here each 

 form is specialized to a distinct function in the 

 economy of the species. Among the higher animals, 

 albinoism and melanism may, as I have already stated, 

 be considered as analogous facts ; and I met with 

 one case of a bird, a species of Lory (Eos fuscata), 

 clearly existing under two differently coloured forms, 

 since I obtained both sexes of each from a single 

 flock, while no intermediate specimens have yet been 

 found. 



The fact of the two sexes of one species differing 

 very considerably is so common, that it attracted but 

 little attention till Mr. Darwin showed how it could 

 in many cases be explained by the principle of 



