'PHYSIOLOGICAL UNITS' 79 



space" that all the apparatus of determinants exist, and that 

 all the provisions are supposed to be made with the aid of special 

 " vital affinities," for the proper " architecture " of the granular 

 ids, and for the fitting " segregation " of determinants throughout 

 all the stages of development of the particular animal or plant ! 



We might go on enumerating several other requirements that 

 would have to be taken into account, relating, for instance, to 

 double sexual determinants ; to the requirements in the case of the 

 dimorphism of larvae ; and the polymorphism often existing in 

 such social insects as ants and bees (See loc. cit., Vol. I, p. 390), 

 Then, again, as each id is presumed to consist of a complex of 

 determinants necessary for the production of a complete individual, 

 as there are many ids in each chromosome and many chromosomes 

 in each nucleus, it follows that there must be a whole host of 

 determinants which would have to find their way into each cell 

 during development, so that very special ' forces ' would need to 

 be called into operation to make the multitude lie low while 

 some chosen determinant (through the ' struggles ' of its liberated 

 biophors) was impressing its special characters upon the previously 

 indifferent embryonal cell. And, looking to this work that the 

 biophors are supposed to perform, it seems clear that there must 

 be a further complication : they must be endowed with mysterious 

 specific qualities. Thus Weismann says, " in any case the biophors 

 which transform the general character of the embryonic cells into 

 the specific character of a particular tissue-cell must themselves 

 possess a specific structure different from that of other biophors, 

 for they must keep up the continuity of structures handed on from 

 ancestors — chlorophyll, and muscle-substance, and the like." 



To be asked to accept anything of this kind as a rational 

 interpretation of what occurs in the development of an individual, 

 must be felt by many to make serious demands upon their faith ; 

 and this strain may give place to actual increduUty when they 

 learn that this whole agglomeration of assumptions and hypo- 

 theses has been built up upon a doctrine which is itself, to say 

 the least, devoid of any firm foundation in fact, and may fairly 

 enough be said to be strongly opposed to many well-known facts 

 — I allude to the author's celebrated and fundamental doctiine as 

 to " the continuity of germ-plasm," and the " immortality of germ 

 cells " which he has advocated since 1885. 



He would have us beUeve that the ordinary cells of the body — 

 the ' somatic cells '—are always quite distinct from the ' repro- 



