n] BIOLOGICAL FOUNDATIONS 57 



and the cell is the historical basis of organic in- 

 dividuality. 



Protoplasm at its first appearance was presumably 

 a homogeneous substance ; as long as it remained so, 

 these masses into which it segregated, however definite 

 their size, their shape, and their reproduction, were 

 yet not individuals. In their working they are like a 

 host of other chemical substances, blindly forging 

 ahead with their reactions, ceasing if the outer con- 

 ditions transgress certain limits, continuing the same 

 as long as they remain Avithin those limits. They are 

 not, in the strict biological sense of the word, adapted 

 to their surroundings 1 , they are not adapted any 

 more than such a cyclical or catalytic reaction as that 

 which takes place in the manufacture of sulphuric 

 acid from sulphur dioxide, water, and oxides of 

 nitrogen. These, much after the fashion of protoplasm 



arisen by internal differentiation (p. 60), so that the lowest non- 

 nucleated moueron, the complex protozoan, and the specialized 

 metazoan tissue-cell are all homologous, and some word is required 

 which will cover them all. Whether a mass of protoplasm is 

 nucleated or not is of importance, but it is of still more importance 

 to know whether it has arisen by a series of divisions from a primary 

 unit of life, and so whether it is itself a primary unit. Such units we 

 shall here call cells. 



1 It will be objected that the change in surface-tension permitting 

 binary fission is adaptive or purposeful. This is quite true, but the 

 adaptation is concerned only with the race ; it is the first step towards 

 a species-individuality. The cells within the species, however, remain 

 unaffected. 



