10 THE FIRST PRINCIPLES OF HEREDITY 



us say, into a limb during the individual development of the 

 embryo should be able, if need be, to perform the same 

 feat again. 



When we come to such cases as the Begonia leaf, where 

 we find the tiniest particle will reproduce the whole plant, 

 we are not very far from reproduction proper. Regenera- 

 tion may be said to be reproduction of a part of the body, 

 while reproduction proper is of the whole body. 



Now, we have seen that Regeneration itself is nothing 

 else than new growth proceeding from the old cells, and 



I n 



Fig. 2. — Regeneration of a Planarian. (After Morgan.) 



[From Weismanfiy " The Evolution Theory.") 



I, transverse ; II, longitudinal section. 



there will therefore at this stage of our inquiry be nothing 

 startling in the statement of Herbert Spencer that " Re- 

 production is discontinuous growth." 



This will be still better understood after studying repro- 

 duction itself in all its phases. 



II.—REPROD UCTION. 



It was pointed out at the beginning of this chapter that 

 the first misunderstanding to be cleared up with regard to 

 reproduction is the popular idea that reproduction means 



