854 



SCIENCE. 



[N. S. Vol. III. No. 76. 



ceed in reinstating this principle in its em- 

 perilled rights it would be a source of ex- 

 treme satisfaction to me." To hear the 

 author of ' Die Allmacht der Naturzilch- 

 tung ' speak of ' ]-ehabilitating ' and ' rein- 

 stating ' the principle of selection betokens 

 a revolution of opinion scarcely less sudden 

 and wonderful than that manifested in a 

 certain historic conversion on the way to 

 Damascus. 



In this paper Weismann expressly makes 

 the following concessions : 1. "The princi- 

 ple of panmyxia is not alone sufficient for a 

 full explanation of the phenomena (of degen- 

 eration). My opponents in advancing this 

 objection are right to the extent indicated 

 and as I expressly acknowledge." 2. " The 

 Lamarckians were right when they main- 

 tained that the factor for which hitherto 

 the name of natural selection had been ex- 

 clusively reserved, viz., personal selection, 

 was insufiQcient for the explanation of the 

 phenomena" (of the disappearance of use- 

 lessparts). 3. " The fact of a simultaneous, 

 functionally concoi'dant yet essentially 

 diversified modification of numerous parts 

 points conclusively to the circumstance that 

 something is still ivanting to the selection of Dar- 

 win and Wallace which it is obligatory on us to 

 discover if we possibly can, and without which 

 selection as yet offers no complete explana- 

 tion of the phyletic processes of transforma- 

 tion. There is a hidden secret to be unrid- 

 dled here before we can obtain a satisfactory 

 insight into the phenomena in question. 

 We must seek to discover ivhy it hap)pens that the 

 useful variations are alioays piresent." 



These are most fundamental concessions, 

 yet it must not be supposed that they 

 necessarily lead to the Lamarck ian position. 

 The insufficiency of natural selection to ex- 

 plain all the phenomena of phj'letic trans- 

 formation Weismann attributes to the fact 

 that this principle has been unduly limited 

 in its field of operation ; it has heretofore 

 been regarded as applicable only to persons; 



it should be considered as applicable to 

 every organic unit, whether visible or in- 

 visible, even down to the hypothetical 

 biophores. 



Natural selection occurs among all orders 

 of individuality, colonies, persons, organs 

 and tissues, determinants and biophores, 

 and corresponding to these different units 

 Weismann recognizes " three principal 

 stages of selection : Thut of j^ersonal selection 

 as it was ennunciated bj' Darwin and Wal- 

 lace; that of /)i's?o»a? selection as it was es- 

 tablished by Wilhelm Eoux in the form of 

 a ' struggle of the parts,' and finally that of 

 germinal selection whose existence and effi- 

 cacy," he says, "I have endeavored to sub- 

 stantiate in this article — these are the fac- 

 tors which have cooperated to maintain the 

 forms of life in a constant state of varia- 

 bility and to adapt them to their conditions 

 of life." In brief, natural selection is still 

 omnipotent if onlj- it be regarded as omni- 

 present. 



Germinal selection consists in an exten- 

 sion of this ijrinciple of selection to the de- 

 terminants and biophores and it may be re- 

 duced to the following propositions : 



1. " Everjf independently and heredita- 

 rily variable part is represented in the germ 

 by a determinative group of vital units, 

 whose size and power of assimilation cor- 

 respond to the size and vigor of the part." 



2. Variations in the size of determinants 

 (some being larger, some smaller and some 

 the same size as the maternal determinants) 

 are caused by ' the inevitable fluctuations 

 of the nutritient supply.' The ultimate cause 

 of all inherited variations in sise is, therefore, to 

 be found in the influence of nutrition on the de- 

 terminants. 



3. The quality of a determinant depends 

 upon the numerical proportion of the bio- 

 phores which it contains. If that propor- 

 tion is altered so also is the character of the 

 determinant. The struggle for nutriment, 

 with its subsequent preference of the strong- 



