XI] CONCLUSION 849 



Again, we find the same forms, or forms which (save for external 

 ornament) are mathematically identical, repeating themselves in all 

 periods of the world's geological history; and we see them mixed 

 up, one with another, irrespective of cHmate or local conditions, in 

 the depths and on' the shores of every sea. It is hard indeed (to 

 my mind) to see in such a case as this where Natural Selection 

 necessarily enters in, or to admit that it has had any share what- 

 soever in the production of these varied conformations. Unless 

 indeed we use. .the term Natural Selection in a sense so wide as to 

 deprive it of any purely biological significance; and so recognise 

 as a sort of natural selection whatsoever nexus of causes suffices 

 to differentiate between the likely and the unlikely, the scarce and 

 the frequent, the easy and the hard: and leads accordingly, under 

 the pecuhar conditions, limitations and restraints which we call 

 "ordinary circumstances," one type of crystal, one form of cloud, 

 one chemical compound, to be of frequent occurrence and another 

 to be rare*. 



* Cf. Bacon, Advancement of Learning, Bk. ii (p. 254) : " Doth any give the reason, 

 why some things in nature are so common and in so great mass, and others so rare 

 and in so small quantity?" 



