138 GENERAL BIOLOGY 



or more vigorous extremities to pursue an individual 

 existence. The development of runners and shoots 

 is a special modification of the same process. 



In the animal realm, one of the simplest examples 

 of budding is found in the common fresh-water 

 Hydra. In this form, the interstitial cells at a 



FIG. 52. Budding Hydra, as seen under the low power of a com- 

 pound microscope: B, attached end; B l , B 2 , buds; M, mouth; T, tenta- 

 cles. (From Hunter's Elements of Biology : American Book Co.) 



certain point begin to increase in numbers, and form 

 a knoblike protrusion on the side of the hydra-body. 

 By a shifting and rearrangement of the cells composing 

 this lump, a cavity forms, in direct communication 

 with the inner cavity of the Hydra. This bud 

 grows until it attains a considerable size, when the 

 cells at the extremity begin to differentiate into ten- 



