208 MISCELLANEOUS OBJECTIONS TO THE 



orbit. The forehead between the eyes consequently becomes, 

 as could be plainly seen, temporarily contracted in breadth. 

 On one occasion Malm saw a young fish raise and depress the 

 lower eye through an angular distance of about seventy 

 degrees. 



We should remember that the skull at this early age is 

 cartilaginous and flexible, so that it readily yields to muscu- 

 lar action. It is also known with the higher animals, even 

 after early youth, that the skull yields and is altered in shape, 

 if the skin or muscles be permanently contracted through 

 disease or some accident. With long-eared rabbits, if one 

 ear flops forward and downward, its weight drags forward 

 all the bones of the skull on the same side, of which I have 

 given a figure. Malm states that the newly-hatched young 

 of perches, salmon, and several other symmetrical fishes, 

 have the habit of occasionally resting on one side at the 

 bottom ; and he has observed that they often then strain 

 their lower eyes so as to look upward ; and their skulls are 

 thus rendered rather crooked. These fishes, however, are 

 soon able to hold themselves in a vertical position, and no 

 permanent effect is thus produced. With the Pleuronectides, 

 on the other hand, the older they grow the more habitually 

 they rest on one side, owing to the increasing 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 distortion would no doubt be in- 

 creased through the principle 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 Trachypterus 

 arcticus, which is not a member of the Pleuronectidae, 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. Gtinther, concludes his abstract of Malm's paper, by 

 remarking that " the author gives a very simple explanation 

 of the abnormal condition 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 



