308 LEISURE-TIME STUDIES. 



ally they exhibited, as adults, no modification or deformity 

 such as they now possess. Assume with Uarwin and the 

 assumption is both reasonable and warranted that the 

 " embryonal (or young) state of each species reproduces 

 more or less completely the form and structure of its less 

 modified progenitors," and we may be taught by the develop- 

 ment of the flat-fishes that they have sprung from ancestors 

 which possessed symmetrical bodies, and that the conditions 

 they present to our notice have certainly been of acquired 

 nature. 



But the question, " How have these abnormal conditions- 

 and modifications of structure been acquired ? " still remains 

 for consideration. It is on this point that Mr. Mivat 

 challenges the adequacy of external conditions and outward 

 influences to produce the characteristic deformities before us. 

 On another occasion this author remarks, " If this condition 

 had appeared at once, if in the hypothetically common 

 ancestor of these fishes, an eye had suddenly become trans- 

 ferred, then the perpetuation of such a transformation by the 

 action of 'Natural Selection' is conceivable enough. Sudden 

 changes, however, are not those favoured by the Darwinian 

 theory, and indeed the accidental occurrence of such a 

 spontaneous transformation is far from probable. But if 

 this is not so, if the transit was gradual, then how such 

 transit of one eye a minute fraction of the journey towards 

 the other side of the head could benefit the individual is 

 indeed far from clear. It seems, even," concludes Mr. 

 Mivart, "that such an incipient transformation must rather 

 have been injurious." So far as these remarks regarding the 

 rarity of sudden variations are concerned, they are perfectly 

 appropriate j although it must at the same time be borne in 

 mind that occasionally startling modifications have appeared 

 in a species of animals in one generation, and without the 

 slightest warning or indication that a sudden alteration was 

 to be produced. A well-known instance of this kind was the 

 sudden appearance of the ancon or otter sheep of Mas- 

 sachusetts, a sheep possessing a long body and short legs, 



