350 PRESENT PROBLEMS IN EVOLUTION AND HEREDITY. 



portion oftlie body which is not essential to life and yet the ]>ower <»f 

 conijjlete reprod action of a new individnal from the germ cells are un- 

 imj^aired. Among the many reasons advanced for pensioning the 

 <irippled soldiers of onr late war yon never hear it nrged that tlieir 

 children are incapacitated by inheritance of injnries. The strongest 

 proof however rests in the evidence I have already cited from hered- 

 ity of the extraordinary stability of the germ cells, which is the safe- 

 guard of tlie race. 



1?. The specific nature of the germ-plasm must be considered before 

 we consider its relations. Wherein lies the conservative power of the 

 germ-plasm, and in what direction shall we look for its tra.nsformiug 

 forces? You see at once that marvellous as is the growth of cells in 

 other tissues, the growth of tlie germ cell is still more so. 



We find it utterly impossible to form any conception of the contents 

 of the microcosmic nucleus of the human fertilized ovum, which is less 

 than one twenty-five-hundredths of an inch in diameter, but which is 

 nevertheless capable of ]iroducing hundreds of thousands of cells like 

 itself, as well as all the unlike cells of the adult organism. We can only 

 translate our ideas as to the possible contents of this nucleus in the 

 terms of chemistry and physics.* 



Spencer t assumed an order of molecules (U' units of protoplasm lower 

 in degree than the visible cell units, to the internal or polar forces of 

 which, and their modification by external agencies and inter-action, he 

 ascribes the ultimate responsibility in reproduction, heredity, and 

 adaptation. This idea of biological units seems to me an essential part 

 of any theory ; it is embodied in Darwin's '• gemumles," in Haeckel's 

 " plastidules 5" yet, as Lankester says the rapid accumulation of bulk is a 

 theoretical difticulty in the material conception of units. In the direc- 

 tion of establishing some analogy between the repetition power of hered- 

 ity and known function of protoplasm, IIaeckel| and Hering§ have 

 likened heredity to memory, and advanced the hypothesis of persist- 

 ence of certain undulatory movements; the undulations being suscep- 

 tible of tihange, and therefore of producing variability, while theirten- 

 dency to x>ersist in their established harmony is the basis of heredity. 

 J^erthold, Gautier, and Geddes|| have s])eculated in the elaboration of 

 the idea of metabolism ; the former holding the view that "inheritance 

 is possible only upon the basis of the fundamental fact that in the 

 chemical processes of the organism the same substances and mixtures 

 of substances are repioduced in (piantity and ([nality with regidar 

 periodicity.'' 11 



*See Ray Lankester, Nature, ,) xi\y 15, 1876. 

 iPrincipJes of Biolo(/!i, vol. i., p. '2o6. 



i Perij/enesis dcr I'lasfidule oder die WeAlenzengmuj dcr Lebcni^thcihlicii. Jena, 1875. 

 V^ Uebir d. Geddchlniss ah vin eallocmeitic Function d. ortjauischcit Matcvic Vienna, 

 1870. 



II See also Thomson, op. cit., ]>. 102. 



IfBerthokl: Studicu iiher I'rolopJdsma-MccltuDik. TiOipsic, 188H. 



