1899] THE SCOPE OF NATURAL SELECTION 123 



was living in ; and lastly, if we were fully acquainted with the char- 

 acter of the organism and its environment it would still be difficult 

 to form any adequate opinion on the value of such a variation, owing 

 to the fact that this apparently simple organism would differ so widely 

 from our own functional activity and life that any conclusions formed 

 on comparative methods of testing its powers, etc., would be extremely 

 likely to be fallacious. If, however, we keep in mind the facts that 

 (1) the whole and not merely a part of the organism is selected, and 

 that, therefore, each variation does not require to be of the same value 

 as if selection depended on it alone ; (2) specialisations are largely 

 quantitative, between man at one extreme of development and a simple 

 unicellular organism at the other, the difference though very great, is 

 mainly due to the fact that man is a huge multicellular colony ; this 

 difficulty will be much simplified. To estimate the qualitative difference 

 it is necessary to endeavour to determine the specialisation of an in- 

 dividual cell in one of those collective specialisations or organs : the 

 difference between a cell in, for instance, the cerebral cortex of man 

 and the character of an amoeba is no doubt great, but the amoeba 

 reacts to stimuli, though in a less specialised form just as the cortex 

 cell does ; in the same way the reaction to light in the mammalian eye 

 is not a new development — it has its beginnings in the preference for 

 light or darkness shown by many unicellular organisms. These two 

 points that selection is organismal and that specialisations are as, or 

 more, largely quantitative than qualitative, weaken if they do not 

 abolish all those difficulties to natural selection that are founded 

 on this objection, and it is further necessary to recollect that no 

 specialisation has yet been found which has not a primitive counter- 

 part in the earliest known forms of life. 



5. The, Imperfections of the Geological Record. — This is obviously 

 a much less important objection than the preceding one. The very large 

 areas of the world that have yet to be examined tend very much to 

 weaken any objection founded on imperfections and absence of links. 

 And as with increasing research these missing links are being steadily 

 filled in, it follows that this objection has become weaker and not 

 stronger with advancing knowledge. 



There are, however, certain points which it is essential to recollect 

 in any consideration of the imperfections arising from this cause. 

 Lloyd Morgan has pointed out that, as the tendency of natural 

 selection is to favour, under appropriate conditions, definiteness both 

 in the soma and in the germinal structures, the geological record should 

 not be expected to provide evidence that does not correspond to this 

 definite line of development. 



There is also another point which does not appear to me to have 

 been sufficiently emphasised. In the earlier part of this paper I drew 

 attention to the fact that Darwin considered the mutual action of a 

 different set of inhabitants arising from the birth of a new generation 



