186 



GENERAL BIOLOGY 



is particularly characteristic of the " lower," i.e. 

 less specialized types. For example, although the 

 leg of a salamander will regenerate as described, 

 as will also that of a frog tadpole, that of a mature 

 frog will not. Regeneration is also found in plants. 

 A leaf of Begonia, if put in water, will grow roots and 

 regenerate the whole plant. From one point of 

 view there is nothing fundamentally different in 



Fio. 67. Regeneration in Hydra: A, normal Hydra (lines show 

 where piece was cut out) ; B, 1-4, changes in a piece of .4 as seen from 

 side ; C, 1-4, same as seen from end ; D, E, F, later changes in same 

 piece. (From Jordan and Kellogg, after Morgan.) 



the differentiation of a tissue-fragment artificially 

 sundered from the organism into a new organism, 

 and the similar differentiation of a tissue-mass 

 (bud) naturally sundered from a parent organ- 

 ism ; or, indeed, of a single cell, whether spore or 

 gamete, thrown off from such an organism. In 

 each case there is the achievement of a certain spe- 

 cific type, by differentiation from an apparently 



