to form Varieties, 



6359 



account, any right to assume that those of which we know so little 

 are in reality as weak as our knowledge of them is small : the only 

 circumstance that can give us a right to conclude this is the fact that 

 they do exert that modifying effect which they would if they were in 

 existence and in active exercise ; and of this fact, in the present 

 instance, we have no proof; indeed the facts of the case seem to me 

 to point, with no unmeaning finger, in the opposite direction — the 

 specific, distinctness of species, closely allied and following each other 

 immediately in the course of time, seems now considered almost a 

 geological axiom ; nor, so far as I am aware, is there in the whole 

 range of natural science, a single instance of indefinite progress, 

 except in the case of man himself ; and here it seems closely connected 

 with, if not entirely dependent upon, his power of abstract conception ; 

 that is, upon that power which forms the grand distinctive mark 

 which separates man from all other organized beings. 



What we want on this subject is the record and collation of facts, 

 experiments and observations ; and if this be done I feel assured that 

 we shall find here, as Kepler did with the irregularities in the orbits of 

 the planets, that the variations return into themselves in constantly 

 recurring cycles. 



With regard to the last paragraph, I am quite at a loss to know what 

 meaning to attach to it. Mr. Wallace says, "This progression by 

 minute steps in different directions, but always checked and balanced 

 by the necessary conditions, subject to which alone existence can be 

 preserved, may, it is believed, be followed out so as to agree with all 

 the phenomena presented by organized beings, their extinction and 

 succession in past ages, and all the extraordinary modifications of 

 form, instinct and habits which they exhibit." Does he mean that by 

 the tendency to vary we may explain all the differences that obtain 

 between different varieties of the same species, or between different 

 species of the same genus, or between different genera of the same 

 order ; or, further still, that we may trace back all organic life, as we 

 see it now, to some unknown root in the far-off geologic ages, some 

 sponge, or polype, or vitalized cell, from which everything has since 

 sprung. The words I have quoted will bear this construction, and if 

 the tendency to vary were a law of indefinite variation, it might carry 

 out this idea ; but, being what it is, simply a tendency, it seems to 

 me that painting such an ideal picture on the subject is like Science 

 sitting down at the feet of Imagination. 



Thomas Boyd. 



17, Clapton Square. 



