12 PROCEEDINGS OF THE AMERICAN ACADEMY 



further to hatch their young, as other fishes do, with the characters 

 of the adult ; instead of leaving for a future period (and a peri,od of 

 great mortality among them) the development of the transfer of the 

 eyes to the right or left, — thus transmitting merely the tendency, and 

 not the thing itself, as we find to be the case in Acalephs (Hybocodon), 

 in the Tunicates, Salpas, in the Gasteropods, in the Polyzoa, &c. Yet 

 this tendency is very well defined ; for we rarely meet with dextral 

 forms when the Flounder is sinistral, or vice versa ; and I have, in 

 our common Flounders, met with no instances of reversal in the course 

 of the development. In Plagusia only did I notice such a reversal, 

 where there was an attempt made in many cases — seven out of fif- 

 teen cases — by the young fish to force the left eye to pass to the 

 right side by lying down on the left, but in no case did this prove suc- 

 cessful ; and, after a while, the young fish showed traces of brain dis- 

 ease, and soon died, usually before the process of transfer of the 

 eye had made much progress, — showing that a violation of the nor- 

 mal mode of transfer cannot readily be made with impunity. This 

 may be the explanation of the rarity of such abnormal cases in the 

 whole family. 



The attempts which I made, both in Plagusia and several of the 

 other species of Flounders, to prevent the transfer of the eye by 

 placing the glass dish at a height over a table, and thus allowing the 

 light to come from below, as well as from all other sides, failed in 

 arresting the transfer. This experiment, likewise, produced no effect 

 in retaining the pigment spots of the blind side longer than in speci- 

 mens struck by the light only normally, from above. 



The habits of young Flounders differ greatly from those of the 

 adult : while the latter are generally more or less sluggish, the young 

 Flounders, when measuring less than a couple of inches in length, are 

 remarkably active, bounding through the water, as it were, and, if 

 disturbed, frequently jumping out of the flat dishes in which I kept 

 them. When this happened, falling from the table to the floor, they 

 often remained a considerable time out of water, without appearing to 

 suffer from their exposure, on being put back into water. 



GiARD has, in the Rev. des Scienc. Nat. for September, 1877, sug- 

 gested that the fundamental cause of asymmetry in the animal king- 

 dom was due to a difference in the strength of the organs of sense ; 

 and he has given, in support of this view, some most ingenious 

 speculations on the asymmetry of Ascidians, of which the Tadpole 

 was transparent, while opaque Tadpoles belonged to symmetrical 

 types ; the position of asymmetrical Ascidians being determined by 



