AXIMALS AND THEIR ENVIRONMENTS. 311 



bones of the head. So that in response to the frequent 

 efforts of the young fish, the lower eye is gradually trans- 

 posed to the side of the body which will hereafter be the 

 uppermost surface, and which will meanwhile have been 

 acquiring its characteristic coloration. Such is the explana- 

 tion given by competent observers of the manner in which 

 the flat-fishes have acquired their strange modifications of 

 structure. The flat-fishes of to-day acquire this modification 

 in virtue of inherited tendencies and of the effect of habit 

 transmitted through many antecedent generations. But the 

 observation of the stages through which the young animals 

 pass in the seas of to-day, reveals a truthful and unerring 

 history of the fashion in which their far-back progenitors 

 inaugurated the first phases in their singular transformations. 

 So far as the explanation of the curious features pre- 

 sented by the flat-fishes goes, it is fully supported by facts as 

 they stand. Additional evidence of weighty kind, however, 

 is obtainable from various sources in favour of Goethe's 

 assertion that form of body " determines the animal's way of 

 life," and that " in turn the way of life powerfully reacts upon 

 all form." The evidence that the deformity in question has 

 been acquired through the material contact of surroundings 

 with the bodies of the first flat-fishes is derived from a two- 

 fold source, firstly, from a view of the various members 

 included in the group of the flat-fishes ; and secondly, from 

 our knowledge of the development of abnormal features in 

 other fishes and in other groups of animals. It would cer- 

 tainly afford some ground for Mr. Mivart's remark, that 

 by "natural selection" we might require to postulate the 

 sudden transference of the lower eye to the upper side of 

 the head, if the flat-fishes were found to present a thorough 

 uniformity and similarity in their deformity. If the whole 

 race or family of these fishes, without a single exception, 

 presented the malformations in a typical degree, then the 

 idea of sudden and sharp modification might be rendered 

 probable enough. But the systematic naturalist would in- 

 form us that these fishes are not uniformly modified. On 



