OBJECTIONS TO THE THEORY 817 



Other, and the whole body is then symmetrical, with both 

 sides equally colored. Soon the eye proper to the lower 

 side begins to glide slowly round the head to the upper 

 side; but does not pass right through the skull, as was 

 formerly thought to be the case. It is obvious that 

 unless the lower eye did thus travel round, it could not 

 be used by the fish while living in its habitual position on 

 one side. The lower eye would, also, have been liable to 

 be abraded by the sandy bottom. That the Pleuronectidse 

 are admirably adapted by their flattened and asymmetrical 

 structure for their habits of life is manifest from several 

 species, such as soles, flounders, etc., being extremely 

 common. The chief advantages thus gained seem to be 

 protection from their enemies, and facility for feeding 

 on the ground. The different members, however, of the 

 family present, as Schiodte remarks, "a long series of 

 forms exhibiting a gradual transition from Hippoglossus 

 pinguis, which does not in any considerable degree alter 

 the shape in which it leaves the ovum, to the soles, 

 which are entirely thrown to one side." 



Mr. Mivart has taken up this case, and remarks that a 

 sudden spontaneous transformation in the position of the 

 eyes is hardly conceivable, in which I quite agree with 

 him. He then adds: "If the transit was gradual, then 

 how such transit of one eye a minute fraction of the 

 journey toward the other side of the head could benefit 

 the individual is, indeed, far from clear. It seems, even, 

 that such an incipient transformation must rather have 

 been injurious." But he might have found an answer to 

 this objection in the excellent observations published in 

 1867 by Malm. The Pleuronectidag, while very young 

 [and still symmetrical, with their eyes standing on oppo- 



