170 THE SCIENCE OF BIOLOGY 



plants in a given generation were inherited in the next; that 

 if an animal used the same parts in the same way, generation 

 after generation, or if it failed to use them, the results were 

 cumulative. Each generation added a little and this was 

 passed on to its offspring. Thus bit by bit the modification 

 was carried to an extreme degree. Lamarck's own formula- 

 tion of his doctrine was complicated by mystical ideas about 

 the animal's willing to do or to be certain things. But its 

 essential claim was that effects produced by use, disuse, and 

 environment were inherited by the next generation. 14 



The Lamarckian theory of the causes of evolution was 

 not widely accepted at the time of its promulgation for the 

 same reason that the entire theory of transmutation was 

 rejected. The opponents of the Lamarckian doctrine 

 criticized not only the proposed causes but also the claim 

 that evolution had occurred. The Lamarckian hypothesis 

 of evolutionary causation has survived to the present day 

 and still finds support from those who are called the Neo- 

 Lamarckians. But it has never been widely accepted. Of 

 late years the failure to obtain conclusive evidence for the 

 inheritance of characteristics acquired by the individual has 

 told heavily against the theory. It would seem that if such 

 inheritance occurs we should by now have secured experi- 

 mental proof. Convincing proofs have not been forth- 

 coming. The majority of biologists, therefore, regard the 

 Lamarckian Theory as distinctly not proved. Many go 



14 Some of the specific cases which Lamarck cites are as follows: The webbed 

 feet of swimming birds were produced by the animals' efforts to spread their 

 toes in attempting to keep afloat; the legs of wading and of perching birds 

 became long or short by their use in these peculiar fashions; snakes lost their 

 limbs through disuse. Snails acquired tentacles by the stimulation of the 

 anterior end of the body, as the animal crawled about and came in contact with 

 obstacles.' Lamarck's most extended statement of his doctrine appears in his 

 "Philosophic Zoblogique." Modern advocacy of Lamarckism will be found 

 in: Packard, A. S., "Lamarck, His Life and Work," 1901; and Henslow, G., 

 "The Origin of Plant Structures," 1895. An excellent, if brief, summary of 

 Lamarckism appears in: Herbert, S., "First Principles of Evolution," pp. 111- 

 116. 



