456 HEREDITY AND DEVELOPMENT 



(or constitutional units, as I would now rename them) as having 

 such natures that while a minute modification, representing some 

 small change of local structure, is inoperative on the proclivities 

 of the units throughout the rest of the system, it becomes operative 

 in the units which fall into the locality where that change occurs." 



4. Furthermore, Spencer supposed " an unceasing circulation 

 of protoplasm throughout an organism," such that " in the course 

 of days, weeks, months, years, each portion of protoplasm visits 

 every part of the body " — a wild assumption. Therefore, " we 

 must conceive that the complex forces of which each constitutional 

 unit is the centre, and by which it acts on other units while it is 

 acted on by them, tend continually to remould each unit into 

 congruity with the structures around ; superposing on it modifica- 

 tions answering to the modifications which have risen in these 

 structures. Whence is to be drawn the corollary that in the course 

 of time all the circulating units — physiological, or constitutional, 

 if we prefer so to call them — visit all parts of the organism ; are 

 severally bearers of traits expressing local modifications ; and that 

 these units, which are eventually gathered into sperm-cells and 

 germ-[egg-]cells, also bear those superposed traits." 



5. According to Spencer, " sperm-cells and germ-[egg-]cells 

 are essentially nothing more than vehicles in which are contained 

 small groups of physiological units in a fit state for obeying their 

 proclivity towards the structural arrangement of the species they 

 belong to"; and "if the likeness of offspring to parents is thus 

 determined, it becomes manifest, a priori, that, besides the trans- 

 mission of generic and specific peculiarities, there will be a trans- 

 mission of those individual peculiarities which, arising without 

 assignable causes, are classed as spontaneous." 



We have illustrated Spencer's position at some length because 

 so many British biologists have recoiled from what they call the 

 complexity of Weismann's theory. But a little consideration 

 will show that the protagonist of British biology invented a 

 system in comparison to which Weismann's is simplicity. 



Nor can we close our exposition without recalling how Spencer 

 confessed that " the actual organising process transcends con- 

 ception. ... It is not enough to say that we cannot know it ; 



