BOTANICAL BIOLOGY. 407 



natural historj'. At the same time, I am far from claimiug- for it the 

 authority of a scieutific creed or even the degree of certainty which is 

 possessed by some of the laws of astronomy. I only affirui that as a 

 theory it has proved itself a potent and invaluable instrument of re- 

 search. It is an immensely valuable induction ; but it has not yet 

 reached such a position of certitude as has been attained by the law of 

 gravitation; and I have myself, in the field of botany, felt bound to 

 protest against conclusions being drawn deductively from it without 

 being subjected to the test of experimental verification. This attitude 

 of mine, which I believe I share with most naturalists, must not how- 

 ever be mistaken for one of doubt. Of doubt as to the validity of Mr. 

 Darwin's views I have none: I shall continue to have none till I come 

 across facts which suggest doubt. But that is a diti'erent position from 

 one of absolute certitude. 



It is therefore without any dissatisfaction that I observe that many 

 competent persons have — while accepting Mr. Darwin's theory — set 

 themselves to criticize various parts of it. But I must confess that I 

 am disposed to share the opinion expressed by Mr. Huxley, that these 

 criticisms really rest on a want of a thorough comprehension. 



Mr. Romanes has put forward a view which deserves the attention 

 due to the speculations of a man of singular subtlety and dialectic skill. 

 He has startled us with the paradox that Mr. Darwin did not after all, 

 put forth — as I conceive it was his own impression he did — a theory 

 of the origin of species, but only of adaptations. And inasmuch as Mv. 

 Romanes is of opinion that specific differences are not even generally 

 adaptive, while those of genera are, it follows that Mr. Darwin only 

 really accounted for the origin of the latter, while for an explanation of 

 the former we must look to Mr. Romanes himself. For my part how- 

 ever, I am altogether unable to accept the premises, and therefore fail 

 to reach the conclusion. Specific differences, as we find them in plants, 

 are for the most part indubitably adaptive, while the distinctive charac- 

 ters of genera and of higher groups are rarely so. Let anyone take the 

 numerous species of some well characterized English genus — for exam- 

 ple, Eanuncul'us ; he will find that one species is distinguished by having 

 creeping stems, one by a tuberous root, one by floating leaves, another 

 by drawn-out submerged ones, and so on. But each possesses those 

 coujmon characters which enable the botanist almost at a glance, not- 

 withstanding the adaptive disguise, to refer them to the common genus 

 Ranunculus. It seems to me quite easy to see, iu fact, why specific 

 characters should be usually adaptive, and generic not so. Species of 

 any large genus must, from the nature of things, find themselves ex- 

 posed to any but uniform conditions. They must acquire therefore as 

 the very condition of their existence, those adaptive characters which 

 the necessities of their life demand. But this rarely affects those marks 

 of affinity which still indicate their original common origin. Probably 

 these were themselves once adaptive, but they have long been overlaid 



