^50 TRANSACTIONS OF SECTION Jt). 



that the symbiosis came about at the iristaiit that amoeboplasm came into exist- 

 ence There is, however, no evidence that cytoplasm by itself can generate 

 ferments All physiological experiments upon the digestion of Protozoa indi- 

 cates that the cytoplasmic body, deprived of the nucleus, cannot initiate the 

 digestive process. Consequently the existence of purely cytoplasmic organisms 

 would seem to be an impossibility. 



For my part, I am unable to accept any theory of the evolution ot the earliest 

 forms of living beings which assumes the existence of forms of life composed 

 entirely of cytoplasm without chromatin. All the results of modern investiga- 

 tions into the structure, physiology, and behaviour of cells on the one hand, 

 and of the various types of organisms grouped under the Protista, on the other 

 hand— the combined results, that is to say, of cytology and protistology— appear 

 to me to indicate that the chromatin-elements represent the primary and original 

 living units or individuals, and that the cytoplasm re|3resents a secondary 

 product. I will summarise briefly the grounds that have led me to this con- 

 viction, and will attempt to justify the faith that I hold; but first I wish to. 

 discuss briefly certain preliminary considerations which seem to me of great, 

 importance in this connection. 



It is common amongst biologists to speak of ' living substance,' this phrase' 

 being preceded by either the definite or the indefinite article— by either 'the ' 

 or 'a.' If we pause to consider the meaning of the phrase, it is to be pre- 

 sumed that those who make use of it employ the term ' substance ' in the usual 

 sense to denote a form of matter to which some specific chemical significance 

 can be attached, which could conceivably be defined more or less strictly by a 

 chemist, perhaps even reduced to a chemical formula of some type. But the 

 addition of the adjective 'living ' negatives any such interpretation of the term 

 'substance,' since it is the fundamental and essential property of any living; 

 being that the material of which it is composed is in a state of continuaL 

 molecular change and that its component s;ubstance or substances are inconstant . 

 in molecular constitution from moment to moment. When the body of a living: 

 organism has passed into a state of fixity of substance, it has ceased, temporarily 

 or permanently, to behave as a living body; its fires are banked or extinguished. 

 The phrase 'living substance ' savours, therefore, of a contradictio in adjecto;. 

 if it is ' living ' it" cannot be a ' substance,' and if it is a ' substance ' it cannot . 

 be ' living.' 



As a matter of fact, the biologist, when dealing with purely biological' 

 problems, knows nothing of a living substance or substances ; he is confronted! 

 solely by living individuals, which constitute his primary conceptions, and the' 

 terms ' life ' and ' living substance ' are pure abstractions. Every living being: 

 presents itself to us as a sharply-limited individual, distinct from other indi- 

 viduals and constituting what may be termed briefly a microcosmic unit, 

 inasmuch as it is a unity which is far from being uniform in substance or 

 homogeneous in composition, but which, on the contrary, is characterised by 

 being made up of an almost infinite multiplicity of heterogeneous and mutually 

 interacting parts. We recognise further that these living individuals possess 

 invariably specific characteristics ; two given living individuals may be so 

 much alike that we regard them as of the same kind or ' species,' or they may 

 differ so sharply that we are forced to distinguish between them specifically. 

 Living beings are as much characterised by this peculiarity of specific individu- 

 ality as by any other property or faculty which can be stated to be an attribute 

 of life in general, and this is true equally of the simplest or the most complex 

 organisms; at least we know of no form of life, however simple or minute, in 

 which the combined features of individuality and specificity are not exhibited 

 to the fullest extent. A living organism may be so minute as to elude direct 

 detection entirely by our senses, even when aided by all the resources furnished 

 by modern science ; such an organism will, nevertheless, exhibit specific pro- 

 perties or activities of an unmistakable kind, betraying its presence thereby 

 with the utmost certainty. The organisms causing certain diseases, for example, 

 are ultra-microscopic, that is to say, they have not been made visible as yet, 

 and an exact description or definition cannot be given of them at the present 

 time ; yet how strongly marked and easily distinguishable are the specific 

 effects produced by the organisms causing respectively measles and small-pox, 

 for instance, each, moreover, remaining strictly true and constant to its 



