152 The Lamarckian Theory 



ciated with the appearance of other peculiarities in 

 the offspring, but this probably means that the agent 

 that effected change in the body was also able at the 

 same time to effect an independent change in the 

 germ-cells. In short, the direct action of modifying 

 agents on the germ-cells along with the body, is one 

 thing, and the specific enregistration in the germ- 

 cells of somatic modifications from the body, is 

 another thing — as yet not demonstrated to the satis- 

 faction of all critics. 



Furthermore, deeply saturating modifications may 

 influence the blood and other fluids of the body, or 

 may alter the rhythm of metabolism so that the pro- 

 duction of internal secretions is affected, and these 

 internal changes in the somatic environment may act 

 as liberating stimuli on the germ-plasm and provoke 

 variations. Prolonged exercise — e.g., in dancing — 

 may lead to an exaggerated production of muscle- 

 forming substance; the tendency to myogenic me- 

 tabolism may spread to other parts of the body, as 

 it often does ; the influence may saturate through the 

 body, and it is conceivable that it may eventually 

 affect the germ-cells in a way so specific that there 

 is increased muscular development of the offspring. 



It must be clearly understood that, while it is very 

 easy to give an account of certain steps in evolution 

 on the Lamarckian assumption that functional and 

 environmental modifications may be in some degree 

 entailed on the offspring, the possibility of giving 

 this account does not prove that the Lamarckian 

 theory is valid. 



