CONFORMITY TO TYPE 251 



units derived from that parent. In the fertilized germ we have two 



froups of physiological units, slightly different in their structures, 

 'hese slightly different units severally multiply at the expense 

 of the nutriment supplied to the unfolding germ, each kind mould- 

 ing this nutriment into units of its own type. Throughout the 

 process of evolution, the two kinds of units, mainly agreeing in 

 their polarities and the form which they tend to build themselves 

 into, but having minor differences, work in unison to produce an 

 organism of the species from which they were derived, but work in 

 antagonism to produce copies of their respective parent organisms. 

 And hence ultimately results an organism in which the traits of the 

 one are mixed with traits of the other." 



"Quite in harmony with this conclusion are certain implica- 

 tions . . . noticed respecting the characters of sperm cells and 

 germ cells. We saw sundry reasons for rejecting the supposition 

 that they are highly specialized cells and for accepting the opposite 

 supposition that they are cells differing from the others rather in 

 being unspecialized. And here the assumption to which we seem 

 driven by the ensemble of the evidence is, that the sperm cells and 

 germ cells are essentially nothing more than the vehicles, in which 

 are contained small groups of physiological units in a fit state for 

 obeying their proclivity toward the structural arrangement of the 

 species they belong to." 



These ' 'units" of which Spencer speaks are regarded as 

 intermediate between the chemical units or molecules and 

 the morphological units or cells. They must be immensely 

 more complicated than the chemical units, and must, 

 therefore, correspond to groups of molecules. The whole 

 organism is supposed to be composed of them, all alike in 

 kind. The germ cells contain small groups of them. 



"The former supposition makes regeneration possible to each suf- 

 ficiently large portion of the body, while the latter gives the germ cell 

 the power of reproducing the whole; inasmuch as the 'polarity' of 

 the 'units' leads to their arrangement in such a way that the whole 

 'crystal,' the organism, is restored or even formed anew. The mere 

 difference in the arrangement of the units alike in kind determines the 

 diversity of the parts of the body, while the distinction between 

 different species and that between different individuals is due to a 

 diversity in the constitution of the units." 



Weismann, in considering Spencer's theory, says that 

 "the assumption of these 'physiological units' does 

 not suffice as an interpretation of heredity; it proves in- 

 sufficient even in interpreting the differentiation of or- 

 gans in simple autogeny, quite apart from the question of 

 amphigonic heredity. But it has the merit of having 

 utilized the smallest vital particles as constituent ele- 



