354 LAMARCK, HIS LIFE AND WORK 



matic is an effort." Hence he regards effort as the 

 immediate source of all movement, and considers that 

 the control of muscular movements by consciousness 

 is distinctly observable; in fact, he even goes to the 

 length of affirming that reflex acts are the product of 

 conscious acts, whereas it is plain enough that reflex 

 acts are always the result of some stimulus. 



Another case mentioned by Lamarck in his Ani- 

 wiaux sans Vertkbres, which has been pronounced as 

 absurd and ridiculous, and has aided in throwing his 

 whole theory into disfavor, is his way of accounting 

 for the development of the tentacles of the snail, 

 which is quoted on p. 348. 



This account is a very probable and, in fact, the 

 only rational explanation. The initial cause of such 

 structures is the intermittent stimulus of occasional 

 contact with surrounding objects, the irritation thus 

 set up causing a flow of the blood, to the exposed 

 parts receiving the stimuli. The general cause is the 

 same as that concerned in the production of horns 

 and other hard defensive projections on the heads of 

 various animals. 



In commenting on this case of the snail. Professor 

 Cleland, in his just and discriminating article on 

 Lamarck, says: 



However absurd this may seem, it must be ad- 

 mitted that, unlimited time having been once granted 

 for organs to be developed in series of generations, 

 the objections to their being formed in the way here 

 imagined are only such as equally apply to the the- 

 ory of their origin by natural selection. ... In 

 judging the reasonableness of the second law of 



