248 



SCIENCE, 



[N. S. Vol. XIV. No. 346. 



level at which it may be cut off. The leg 

 of a crab also regenerates at a large number 

 of different levels, and apparently this holds 

 for all the different appendages. If this re- 

 sult had been acquired through the action 

 of natural selection, what a vast process of 

 selection must have taken place in each 

 species ! Moreover, since the regeneration 

 may be complete at each level and in each 

 appendage without regard to whether one 

 region is more liable to injury than is an- 

 other, we find in the actual facts themselves 

 nothing to suggest or support such a point 

 of view. 



If, leaving the adult organism, we examine 

 the facts in regard to regeneration of the 

 embryo, we find again insurmountable ob- 

 jections to the view that the process of 

 regeneration can have been produced by 

 natural selection. The development of 

 whole embryos from each of the first 

 two or first four blastomes can scarcely 

 be accounted for by a process of natural 

 selection, and this is particularly evident 

 in those cases in which the two blastomeres 

 can only be separated by a difficult opera- 

 tion and by quite artificial means. If a 

 whole embryo can develop from an isolated 

 blastomere, or from a part of an embryo 

 without the process having been acquired 

 by natural selection, why apply the latter 

 interpretation to the completing of the adult 

 organism ? 



Several writers on the subject of regener- 

 ation in connection with the process of 

 autotomy (or the reflex throwing off of 

 certain parts of the body) have, it seems 

 to me, needlessly mixed up the question of 

 the origin of this mechanism with the 

 power of regeneration. If it should prove 

 true that in most cases the part is thrown 

 off at the region at which regeneration 

 takes place to best advantage, it does not 

 follow at all that regeneration takes place 

 here better than elsewhere, because in this 

 region a process of selection has most often 



occurred. The phenomenon of regenera- 

 tion in the arm of the starfish, that has 

 been described on a previous page shows 

 how futile is an argument of this sort. If, 

 on the other hand, the autotomy is sup- 

 posed to have been acquired in that part of 

 the body where regeneration takes place to 

 best advantage, then our problem is not 

 concerned with the process of regeneration 

 at all, but with the origin of autotomy. If 

 the attempt is made to explain this result 

 also as the outcome of the process of 

 natural selection acting on individual vari- 

 ations, many of the criticisms advanced in 

 the preceding pages against the supposed 

 action of this theory in the case of regener- 

 ation, can also readily be applied to the case 



of autotomy. 



T. H. Morgan. 



S03IE CONDITIONS INFLUENCING SUCCESS 

 AT SCHOOL. 



The law of universal variation as demon- 

 strated by the pupils of our public schools 

 has presented a most difficult problem to 

 the superintendent. He is ' between the 

 devil and the deep sea ' in his attempts to 

 give the individual his rights, and at' the 

 same time conform to a system which is 

 capable of turning out good material in 

 large quantities. Procrustean beds, with 

 semi- elastic foot-boards are about the best 

 that can be provided for the little folks 

 in the large cities, even under the best con- 

 ditions. The problem is an important one 

 and far from a satisfactory solution, but we 

 have all confidence in the brains which are 

 brought to bear upon it, and it cannot be 

 very long before some one of the systems 

 which are now in the experimental stage 

 will show itself Avorthy of more extended 

 adoption. Whatever variety there may be 

 in the attempts to solve this problem of 

 promotion in the schools — for after all, it re- 

 solves itself to that — there are certain facts 



