598 



SCIENCE. 



[N. S. Vol. I. No. 22. 



volopment so as to build up anew the ar- 

 rangement of pai'ts seen iu the parent tj'pe. 

 This elaborate system of preformationism is 

 bound to produce a reaction that is already- 

 becoming apparent ; in fact, it is probable 

 that its very complexitj^, its many incon- 

 sistencies, as well as the numerous subsid- 

 iary hypotheses that must be worked out to 

 support it, will be fatal to it as a system. 



The path along which the solution of the 

 problem of heredity is to be effected lies in 

 a wholly different direction, namelj^, in 

 that of the study of the mechanics and dy- 

 namics of development, and in the resolute 

 refusal to acknowledge the existence of 

 anything in the nature of preformed organs 

 or of infinitesimal gemmules of any kind 

 whatsoever. Such devices are unnecessary 

 and a hindrance to real progress in the so- 

 lution of the questions of inheritance. 

 They only serve to divert the attention of 

 the observer from the real phenomena in 

 their totality to a series of subordinate de- 

 tails, as has happened in Weismann's case. 

 All this while he has been watching the re- 

 sults of an epigenetic process, as displayed 

 by an inconceivably complex mechanism in 

 continuous transformation, and out of all of 

 this the most essential thing he has wit- 

 nessed has been one of the effects of the oj)- 

 eration of that contrivance in the mere 

 splitting of chromosomes that are his ' ids,' 

 ' idants,' ' biophors,' etc. The potentiality 

 of the part has been mistaken for that of 

 the whole. 



We must dismiss from our minds all im- 

 aginary corpuscles as bearers of hereditary 

 powers, except the actual chemical meta- 

 meric or polymeric molecules of living mat- 

 ter, as built up into ultramicroscopic struc- 

 tures, if we wish to frame an hj'pothesis of 

 heredity that is in accord with the require- 

 ments of dynamical theory. The ' discover- 

 ing' and naming of 'ids,' 'biophors' and 

 ' pangenes' time will show to have been 

 about as profitable as sorting snowflakes 



with a hot spoon. We must also dismiss 

 the idea that the powers of development 

 are concentrated in some particular part of- 

 the germ-cell, nor can we assiime the latter 

 to be homogenous.* This we are compelled 

 to denj' on the ground of the organization 

 of the egg itself. Nor is it possible to deny 

 the reciprocal effects of cells upon each 

 other ; the parts are reciprocals of the whole, 

 as the latter is reciprocal to a j)art. The 

 organism during everj' phase of its existence 

 is a molecular mechanism of inconceivable 

 complexity, the sole motive force of which 

 is the energy that may be set free by the 

 coordinated transformation of some of its 

 molecules by metabolism. An appeal to 

 anything beyond this and the successive 

 configurations of the molecular system of 

 the germ, as a whole, resulting from the 

 changing dj^namical properties of its mole- 

 cules, as their individual configurations and 

 arrangement change, must end in disap- 

 pointment. We must either accept such a 

 conclusion or denj' that the principle of the 

 conservation of force holds in respect to 

 the behavior of the ultimate molecular con- 

 stituents of living substance. But to deny 

 that that principle is operative in living 

 creatures is to question direct experimental 

 evidence to the contrary, since Eiibner has 

 been able to actually use an organism as a 

 faii'lj'' accurate calorimeter. 



The initial configuration or mechanical 

 arrangement and successive rearrangements 

 of the molecules of a germ, the addition of 



*The ivriter finds himself unable to agi-ee with 

 Haacke, it he has properlj' understood that author's 

 assumption as to the homogeneity or monotonous 

 character of living matter, as set forth iu his admir- 

 able work GestaUung nnd Vererbung, 1893. Nor does 

 it aijpear that anything is gained by the acceptance 

 of Haaoke's theory of Gemmaria that is not easily 

 understood upon the far simpler grounds that will be 

 set forth here, though there is much in the book cited 

 with which epigeuesists must agree, ajside from the 

 weighty character of its criticisms and its pregnant 

 suggestiveness. 



