SOME ASPECTS OF GEOLOGIC TIME 267 



admitted that the formation of exterior protective lime coatings 

 is likely to render further developments both difficult and 

 unnecessary. The one notable instance of the higher develop- 

 ment of such invertebrate forms, the cephalopods, has only 

 taken place as and when the protective coating has obsolesced. 

 Thus we have further evidence in favour of our conclusion 

 that this aspect of the relation between organic evolution and 

 geologic time is not likely to give us tangible and certain con- 

 clusions. The probability we have already noted, that pre- 

 Cambrian time is at least of the same order as post-Cambrian, 

 is, however, a valuable result to glean from a first cursory glance 

 at main principles. 



B. Geologic Time and Biologic Theory 



Our results, so far, are interesting but scanty. The biologist 

 can give us much useful information, but his conclusions must 

 not be pressed too far. It will now be interesting to consider 

 the converse, i.e. the effect of our knowledge of geologic time on 

 biologic theory. Much has been written of late years concern- 

 ing theories of evolution, and recent speculations on geologic 

 time have been used as a controversial weapon. The arguments 

 of a class of biologist runs somewhat on the following lines : 

 Natural selection, as postulated by Darwin, requires a great 

 vista of time in which to work. Use-inheritance, which was 

 accepted, not only by the early evolutionists and by Herbert 

 Spencer, but by Darwin himself, has been thought to have been 

 disproved by Weismann and his followers. Therefore the 

 theorist, to escape from the dilemma, has made the inference 

 that evolution has proceeded discontinuously by a succession 

 of "sports" which have happened to be of advantage in the 

 struggle for existence. The inference receives some support 

 from the discoveries of Mendel, which have recently been 

 brought into such prominence by Prof. Bateson and others. 



We cannot here discuss the evidence for and against use- 

 inheritance. In case the reader should suspect bias on grounds 

 not stated here, it may be as well to state that I should classify 

 myself as neo-Lamarckian, and that I do not attach great im- 

 portance to Mendel's discoveries — at any rate, in their relation 

 to the problem now before us. While there can be no doubt 

 concerning Mendel's facts, and the interesting light they throw 

 on some problems of heredity, the evolutionary and theoretical 



