OTHER THEORIES OF SPECIES-FORMING. 223; 



possess a capacity for growth or self-reproduction ; second, the gen- 

 eratules, which have no particular functional work to perform but can 

 grow and reproduce themselves and can carry over this capacity of 

 reproduction to the ergatules, because they can fuse with them or 

 attach themselves to them and thus carry over to them their char- 

 acteristic peculiarities. These generatules are looked on as the: 

 chemical radical of the ergatules, and become therefore the directly- 

 determining agents for all peculiarities of the body. The ergatules 

 sit chiefly in the cytoplasm of the cell, while the generatules lie in the 

 cell nucleus, especially in the chromosomes, and therefore render 

 these the bearers of hereditary characteristics. 



Thus baldly and wholly incompletely stated these theories of 

 ultimate plasm structure which shall be of a sort to agree with all- 

 trie varied phenomena of life, and particularly those of heredity,, 

 show, unfortunately, only their fantastic face. For as it is pre- 

 cisely in showing how the postulated structure and properties are 

 perfectly consonant with all the known phenomena of life that 

 these theories have their actual interest and strength, a fantastic 

 and improbable face shown as to this robs them of all interest. But, 

 perhaps, it is well that the fantastic aspect of them should be first 

 recognised. For it is only fair to say that the ingenuity and plausi- 

 bility, the precise and exhaustive development of detail, of some of 

 these theories, are really dangerous to the layman who first happens 

 to read a full and well-stated account of one of them by an enthu- 

 siastic upholder. One's eyes become closed to the fact that all the 

 structure and performance that seem so natural, and fit in so 

 exactly with all that we actually know of the phenomena of life, 

 have not been seen, only imagined. One needs an introduction to 

 these theories which insists above all on their wholly hypothetical 

 character. Otherwise one is surprisingly readily hypnotised into 

 accepting one or the other of them as a statement of fact. These 

 general theories are the atomic theories of biology without one- 

 tenth the probability of truth or one-tenth the actual acceptance 

 in science that the atomic theory of the chemists has. And even 

 that is beginning to be discarded in modern chemistry. These 

 theories are, as Weismann has said, the outcome of the fact that 

 ''the deeper one studies into the phenomena of heredity, the more 

 one is convinced that something of this kind of a condition [of a 

 composition of the fundamental life substance out of ultra-micro- 

 scopic units bearing a certain spatial relation, and one of attractions 

 and repulsions to each other] must really exist : for it is impossible 

 to explain the observed phenomena in any other way. that is, by 

 any much simpler assumption." But on the other hand a sufficient 

 reason against accepting any one of these highly developed theories 



