THEORIES OP NATURAL SELECTION AND DESIGN. 41 



condition of time for all this was awanting. The lower 

 Silurian trilobites suddenly appear in the geological record as 

 suddenly as the cepJialopoda which, came later, and which stand 

 very much in this respect in relation to other mollusca as the 

 trilobites do to other Crustacea. 



Facts in the life history of recent forms are equally suggest- 

 ive. We take the molecule as the ultimate unit of vitalised 

 substance, and the cell as the expression of aggregate mole- 

 cules, and we follow the action of the differentiating force in 

 the living animal form till we see the mature organism. In 

 its upward working, say from molecule to man, it has utilised 

 diverse, equally with identical, elements in order to identical 

 results. Is there any adequate explanation of this outside of 

 the recognition of intelligent guidance — forethought — some- 

 where, anticipating a definite organism and foresight in 

 providing the means to its realisation and succession ? And, 

 in view of all this, tendencies to variation of every sort have 

 been overcome and limited to secure, we might say, per- 

 manence of species, but we say only persistence of indivi- 

 duality, that we may recognise the element of unlikeness ever 

 characteristic of this. Because, be the guidance what it may, 

 it does not determine perfect resemblance either among the 

 embryonic stages of an organism or among mature forms of 

 the same species. " Advanced Darwinians, ^^ said Agassiz, 

 " are reluctant to acknowledge the intervention of an intel- 

 lectual power in the diversity which obtains in nature, under 

 the plea that such au admission implies distinct creative acts 

 for every species. What of it if it were true ? Have those 

 who have objected to repeated acts of creation ever considered 

 that no progress can be made in knowledge without repeated 

 acts of thinking ? And what are thoughts but specific acts of 

 the mind ? Why should it, then, be unscientific to infer that 

 the facts of nature are the i-esult of a similar process, since 

 there is no evidence of any others ?^' {Agassiz, in Atlantic 

 Montldy, January, 1874, p. 101.) 



If the plea for natural selection as against the theory of 

 design were likely to find illustrative instances in any one 

 biological department more than another, we might expect 

 them among the -protozoa , in which the plasticity of the 

 life substance is most intense, and the mature forms most 

 open to influences, internal and external, towards variation, — 

 a department in which natural selection might be presumed to 

 have widest and freest scope. Yet it is not so. 



To affirm that the highest animal holds something in which 

 the lowest can have no part is self-evident ; but to affirm that 



