238 



SCIENCE. 



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



as the mere outcome — which is to some 

 extent unforeseen — of the physical nature of 

 an animal. Some statements which have 

 been made on this subject seem hardly to 

 admit of any but the latter explanation." 

 After showing that some newts confined in 

 aquaria attacked each other, " and several 

 times one of them siezed another by the 

 lower jaw, and tugged and bit at it so 

 violently that it would have been torn off if I 

 had not separated the animals,''^ ^ and after re- 

 ferring to the regeneration of the stork's 

 beak, Weismann concludes: ''Such cases, 

 the accuracy of which can scarcely be 

 doubted, indicate that the capacity for re- 

 generation does not depend only on the 

 special adaptation of a particular organ, but 

 that a general power also exists which be- 

 longs to the whole organism, and to a cer- 

 tain extent affects many and perhaps even 

 all parts. By virtue of this power, more- 

 over, simple organs can be replaced when 

 they are not specially adapted for regenera- 

 tion." The perplexity of the reader, as a 

 result of this temporary vacillation on 

 "Weismann 's part, is hardly set straight by 

 the general conclusion that follows on the 

 same page : " We are, therefore, led to in- 

 fer that the general capacity of all parts for 

 regeneration may have been acquired by 

 selection in the lower and simpler forms, 

 and that it gradually decreased in the 

 course of phylogeny in correspondence with 

 the increase in complexity of organization ; 

 but that it may, on the other hand, be in- 

 creased by special selective processes in 

 each stage of its degeneration, in the case of 

 certain parts which are physiologically im- 

 portant and are at the same time frequently 

 exposed to loss." 



There are certain statements of facts in 

 this chapter that are incorrect, and the 

 argument is so loose and vague that it is 

 diflScult to tell just what is really meant. 

 As a misstatement of fact I may select the 



*The italics are, of course, my own. T. H. M. 



following case. It is stated that lumbricu- 

 lus does not have the power of regenerating 

 laterally if cut in two, and it is argued that 

 a small animal of this form could rarely 

 be injured at the side without cutting the 

 animal completely in two. As a matter of 

 fact, lumbriculus can regenerate lateially, 

 and very perfectly, as any one can verify if 

 he takes the trouble to perform the experi- 

 ment ; but, of course, if the whole animal is 

 split in two lengthwise the pieces die, or if 

 a very long piece is split from one side the 

 remaining piece usually disintegrates. If, 

 however, the anterior end is split in two for 

 a short distance, or if a piece is partially 

 split in two, the half remaining in contact 

 with the rest of the piece completes itself 

 laterally. The same result follows also in 

 the earthworm. 



As an example of looseness of expression I 

 may quote the following from Weismann : 

 " A useless or almost useless rudimentary 

 part may often be injured or torn ofi" with- 

 out causing -processes of selection to oceur which 

 would produce in it a capacity for regeneration. 

 The tail of a lizard again, which is very 

 liable to injury, becomes regenerated be- 

 cause as we have seen it is of great impor- 

 tance to the individual and if lost its owner 

 is placed at a disadvantage." And as an 

 example of vagueness, the following state- 

 ment commends itself: " Finally the com- 

 plexity of the individual parts constitutes 

 the third factor which is concerned in regu- 

 lating the regenerative power of the part in 

 question ; for the more complex the struc- 

 ture is, the longer and the more energetically 

 the process of selection must act in order 

 to provide the mechanism of regeneration, 

 which consists in the equipment of a large 

 number of different kinds of cells with the 

 supplementary determinants which are ac- 

 curately graduated and regulated as regards 

 their power of multiplication. " 



Without attempting to disentangle the 

 ideas that are involved in these sentences, 



