222 LAMARCK AND DARWIN 



to the new individuals that descend from the individual so 

 modified " (pp. 151-2). 



It is mainly but not entirely by reason of the first of these 

 laws that organisation tends to progress, and mainly by 

 reason of the second and third that difference of environment 

 brings about diversity of organisation. In virtue of the 

 fourth law the acquirements of the individual become the 

 property of the race. 



Lamarck's exposition of his first law, that life tends by its 

 own powers to enlarge and extend its bodily instrument, is 

 vague and difficult to understand. He has already explained 

 some pages back how the first organisms arose by spontaneous 

 generation in the form of minute gelatinous utricles (cf. 

 Oken). He conceives that it is in the movements of the 

 fluids proper to the organism that the power resides to 

 enlarge and extend the body. Nutrition alone is not 

 sufficient to bring about extension ; a special force is required, 

 acting from within outwards (p. 153). In the most primitive 

 organisms the movements of the vital fluids are weak and 

 slow, but in the course of evolution they gradually accelerate, 

 and, becoming more rapid, trace out canals in the delicate 

 tissue which contains them, and finally form organs. 



Subtle fluids play a great part in Lamarck's biology : 

 they take the place of the soul or entelechy which the 

 vitalists would postulate to explain organic happenings. 

 Lamarck seems in this to follow certain of the old materialists, 

 who conceived the soul to be formed of a matter more subtle 

 than the ordinary. 1 



In his second law Lamarck's essentially vitalistic attitude 

 comes out very clearly, for it states that a psychological 

 moment enters into all new production of form, that the 

 ultimate cause of the development of new form is the need 

 felt by the organism. This need is of course not a conscious 

 one, it is a need perceived by the sentiment inte'ricnr. 



1 For instance, Lucretius : 



" Is titii nunc animus <|iuli sit mrpon- ft limit- 

 constiteril pcn^mi rationcm rc<Mrn- ilictis. 

 Prinripi" i-- e aio persubtilem atquc mimitis 

 pi-ii|ii:ini corporibus fartum constare." 



Hi- /\,-i //>n \iiitir<i, iii., w. 177-80. 



