56 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



upon the original symmetrical constitution of the fish at some time 

 in the larval stage as a result of conditions acting on that stage. 

 If we look to the germ, then, we should find in it no evidences of 

 asymmetery, if the Lamarckian theory be the true hypothesis. But, 

 on the contrary, evidence adduced above has shown that there is an 

 asymmetry in the egg which could not have been produced by 

 external forces and which appears at so early a stage that it could not 

 have been produced by the direct effect of "use and disuse." The 

 argument of the Lamarckians, in order to escape from this difficulty 

 would be, of course, that the modifications of the larval and adult 

 stages, which had become fixed by the cumulative effect of repeated 

 actions, became reflected back into earlier and earlier stages until 

 finally the germinal organization itself had become definitely and 

 permanently affected. Of course there is no evidence at present 

 known which will enable anyone to deny positively that such might 

 be the case or that it might thus be capable of explaining the facts 

 in question, but it would certainly seem that the theory would have 

 to be stretched beyond its limits if we are required to believe that 

 if a flat-fish turns over on its right side until the tendency became 

 fixed, the effect of this process on the germinal structure would be to 

 produce an oil-globule in the egg, while if the fish turns over on its 

 left side through a sufficient number of generations, the effect is 

 such as to produce no oil-globule in the egg. It is scarcely less 

 difficult to admit that the asymmetry having become fixed in 

 the larva and adult stages as a result of voluntary attempts at 

 adaptation through a series of generations might become reflected 

 back into such a very early period in the germ as to affect the direc- 

 tion of the growth of the eye-stalk which, at any time, is only in- 

 directly affected by "use and disuse" and only at a very much later 

 stage. But even if we admit this as a possibility, it seems difficult 

 to reconcile this hypothesis with the condition found in the soles, in 

 which the asymmetry has gone considerably further, but has not been 

 able to bring about any constant relation of the optic nerves in the 

 chiasma. 



