OBJECTIONS TO THE THEORY 319 



flatness of their bodies, and a permanent effect is thus 

 produced on the form of the head, and on the position 

 of the eyes. Judging from analogy, the tendency to dis- 

 tortion would no doubt be increased through the prin- 

 ciple of inheritance. Schiodte believes, in opposition to 

 some other naturalists, that the Pleuronectidse are not 

 quite symmetrical even in the embryo; and if this be 

 so, we could understand how it is that certain species, 

 while young, habitually fall over and rest on the left 

 side, and other species on the right side. Malm adds, 

 in confirmation of the above view, that the adult Tra- 

 chypterus arcticus, which is not a member of the Pleuro- 

 nectidse, rests on its left side at the bottom, and swims 

 diagonally through the water; and in this fish, the two 

 sides of the head are said to be somewhat dissimilar. 

 Our great authority on Fishes, Dr. Giinther, concludes his 

 abstract of Malm's paper by remarking that "the author 

 gives a very simple explanation of the abnormal condi- 

 tion of the Pleuronectoids. " 



We thus see that the first stages of the transit of the 

 eye from one side of the head to the other, which Mr. 

 Mivart considers would be injurious, may be attributed 

 to the habit, no doubt beneficial to the individual and to 

 the species, of endeavoring to look upward with both 

 eyes while resting on one side at the bottom. We may 

 also attribute to the inherited effects of use the fact of 

 the mouth in several kinds of fiat-fish being bent toward 

 the lower surface, with the jaw bones stronger and more 

 effective on this, the eyeless side of the head, than on 

 the other, for the sake, as Dr. Traquair supposes, of 

 feeding with ease on the ground. Disuse, on the other 

 hand, will account for the less developed condition of the 



