2 THE GERM-PLAS.M 



' 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 

 units alike in kind determines the diversity of the parts of the 

 body, while the distinction between different species and that 

 between ditferent individuals is due to a diversity in the con- 

 stitution of the units. 



The units of an individual are therefore to a certain extent pro- 

 tean. Thev are capable of arranging themselves in an immense 

 \arietv of wavs. and so form the most diverse cells, tissues, 

 organs, and parts of the body. But they only do this under the 

 directing influence of the whole, in such a way that the whole 

 forces the units of one part to arrange themselves in just such 

 a way as is necessary for the perfection of that part, — a perfec- 

 tion required for the harmony of the whole. Spencer himself 

 says very rightly, ' It seems difficult to conceive that this can 

 be so, but we see that it is so.' As a matter of fact, groups of 

 units removed from an organism possess the power of construct- 

 ing the whole anew : and we are thus obliged to admit that the 

 tendency to take a specific form is present in all parts of the 

 organism. The 'units' are physiologically variable quantities, 

 which in every case act in such a manner as the whole demands. 



The assumption of these * physiological units ' does not suffice 

 as an e.xplanation of heredit}- : it proves insufficient even as 

 interpreting the differentiation of organs in simple ontogeny, 

 quite apart from the question of amphigonic heredity. But it 

 has the merit of having util:.-ed the smallest vital particles as/ 

 constituent elements of the organism, and of having made them] 

 the basis of a theory of heredity. f 



Ernst Briicke was the first to admit the existence of small vitaf 

 particles of this kind, and to give cogent reasons for so doing/ 

 Although he did not denote them bv any special name in hf 

 extremely important paper entitled • Elementar Organismen," * h 

 was the first to oppose the old theory of the cell, especially witl 

 regard to its fluid contents, and to show that its bodv must pr- 

 sess an organisation, quite distinct from the molecular structu 

 of the organic compounds. 



Darwin's theory of ' pangenesis " was stated in the final chap*^' 

 of his great work on • The Variation of Animals an^ 



* ' Wiener Sitzungsberichte,' Oct. lo, 1861, Bd. 



X/ 



