CH^/-. XX. OF VARIATION AND PROGRESSION. 391 



i»lex sti'ucture, aud from the lowest instincts up to the highest, 

 and, finally, from brute intelligence to the reasoning powers 

 of Man. The improvement in the grade of being had been 

 slow and continuous, iind the human race itself was at length 

 evolved out of the most highly organized and endowed of the 

 inferior mammalia. 



In order to explain how, after an indefinite lapse of ages, so 

 many of the lowest grades, of animal or plant, still abounded, 

 he imagined that the germs or rudiments of living things, 

 which he called monads, were continually coming into the 

 world, and that there were diiferent kinds of these monads for 

 each primary division of the animal and vegetable kingdoms. 

 This last hypothesis does not seem essentially different from 

 the old doctrine of equivocal or spontaneous generation ; it 

 is wholly unsupported by any modern experiments or observa- 

 tion, and therefore affords us no aid whatever in speculating 

 on the commencement of vital phenomena on the earth. 



Some of the laws which govern the appearance of new 

 varieties were clearly pointed out by Lamarck. He re- 

 marked, for example, that as the muscles of the arm become 

 strengthened by exercise or enfeebled by disuse, some organs 

 may in this way, in the course of time, become entirely 

 obsolete, and others previously weak become strong and 

 play a new or more leading part in the organization of a 

 species. And so with instincts, where animals experience 

 new dangers they become more cautious and cunning, and 

 transmit these acquired faculties to their posterity. But, not 

 satisfied with such legitimate sj)eculations, the French philo- 

 sopher conceived that by repeated acts of volition animals 

 might acquire new organs and attributes, and that in plants, 

 which could not exert a will of their own, certain subtle 

 fluids or organizing forces might operate so as to work out 

 analogous effects. 



After commenting on these purely imaginary causes, I 



2fj 



