124 SCIENCE PROGRESS. 



the multicellular organism but not of " the organism ". The 

 same fallacy runs throughout the whole argument ; it is the 

 ignoratio elenchi, the attempt to disprove what was not 

 asserted. The existence of this fallacy makes it unneces- 

 sary to follow Whitman's argument in detail ; it need only 

 be said that by the great majority organisation, even a very 

 considerable complexity of visible structure, is readily con- 

 ceded to the single cell. To deny this would be to deny 

 a patent fact. It follows that structure is not dependent on 

 cell division (whoever said it was), and that " formative pro- 

 cesses," whatever that may mean, cannot therefore be re- 

 ferred to cell division, but it does not follow that they are 

 not in some measure due to cellular interaction in multicel- 

 lular animals or that they are due to ultimate elements of 

 living matter, idiosomes, which make up all living matter, 

 are the bearers of heredity and the real builders of the 

 organism. This is the evolution standpoint again. Whit- 

 man must have his idiosomes to explain what he found 

 inexplicable in cells, but what explains the behaviour of 

 idiosomes, how are they, any more than cells, the bearers of 

 heredity and the real builders of the organism ? It is a 

 problem, he tells us, on which we must wait for more light 

 — it is certainly wanted, for the obscurity attending idio- 

 somes or any other biological units is very great. 



Difficult as it has been to give a comprehensive account 

 •of the many theories now current, to account for the pheno- 

 mena of heredity, which are seen to be associated with de- 

 velopment, I have I think made it abundantly clear that 

 there is a general tendency to assume the existence of ulti- 

 mate structural units as necessary for the explanation of 

 vital phenomena. The reasons for this tendency are very 

 succinctly expressed in a sentence of Whitman's, who 

 asserts that it is an accepted axiom that function presup- 

 poses structure. This is a statement of the morphological 

 standpoint ; let us examine it a little further. The varied 

 functions of cells presuppose structures in cells correspond- 

 ing to the functions ; not molecular structures, but definite 

 form elements, themselves of great molecular complexity— in 

 short, an organisation. But the form elements are on all 



