THE FACTORS OF ORGANIC EVOLUTION. 755 



of the past is to be sought in the study of the present, into the position of an 

 axiom ; and the wild speculations of the catastrophists, to which we all listened 

 with respect a quarter of a century ago, would hardly find a single patient hearer 

 at the present day." 



Of the party above referred to as not satisfied with this concep- 

 tion described by Professor Huxley, there were two classes. The 

 great majority were admirers of the Vestiges of the Natural History 

 of Creation — a work which, while it sought to show that organic evo- 

 lution has taken place, contended that the cause of organic evolution 

 is " an impulse " supernaturally " imparted to the forms of life, ad- 

 vancing them . . . through grades of organization." Being nearly 

 all very inadequately acquainted with the facts, those who accepted 

 the view set forth in the Vestiges were ridiculed by the well-instructed 

 for being satisfied with evidence, much of which was either invalid or 

 easily cancelled by counter-evidence, and at the same time they ex- 

 posed themselves to the ridicule of the more philosophical for being 

 content with a supposed explanation which was in reality no explana- 

 tion — the alleged " impulse " to advance giving us no more help in 

 understanding the facts than does Nature's alleged " abhorrence of a 

 vacuum" help us to understand the ascent of water in a pump. The 

 remnant, forming the second of these classes, was very small. While 

 rejecting this mere verbal solution, which both Dr. Erasmus Darwin 

 and Lamarck had shadowed forth in other language, there were some 

 few who, rejecting also the hypothesis indicated by both Dr. Darwin 

 and Lamarck, that the promptings of desires or wants produced 

 growths of the parts subserving them, accepted the single vera causa 

 assigned by these writers — the modification of structures resulting 

 from modification of functions. They recognized as the sole process 

 in organic development the adaptation of parts and powers consequent 

 on the effects of use and disuse — that continual moulding and remould- 

 ing of organisms to suit their circumstances, which is brought about 

 by direct converse with such circumstances. 



But while this cause accepted by these few is a true cause, since 

 unquestionably during the life of the individual organism changes of 

 function produce changes of structure ; and while it is a tenable hy- 

 pothesis that changes of structure so produced are inheritable, yet it 

 was manifest to those not prepossessed, that this cause cannot with 

 reason be assigned for the greater part of the facts. Though in plants 

 there are some characters which may not irrationally be ascribed to 

 the direct effects of modified functions consequent on modified circum- 

 stances, yet the majority of the traits presented by plants are not to 

 be thus explained. It is impossible that the thorns by which a briar 

 is in large measure defended against browsing animals, can have been 

 developed and moulded by the continuous exercise of their protective 

 actions ; for in the first place, the great majority of the thorns are 



