THE HIGHER ORGANISMS 115 



number of individuals, we next pass into congeries of 

 cells in which the identity of each is preserved, though 

 no apparent utility is subserved thereby. This is seen, 

 for example, in Spirogyra, where hundreds of organisms 

 may adhere to one another, in Epistylus, Carchesium, 



FIG. 38. Microgromia socialis. A, Colony of individuals in extended state, 

 some of them undergoing transverse fission; B, colony of individuals (some of 

 them separated from the principal mass) in compact state; C, D, formation and 

 escape of swarm-spore, seen free at E. (Carpenter.) 



and other infusoria where organisms resulting from the 

 division of the parent cell remain attached by their 

 pedicles to a common stalk. A less fixed colonial aggre- 

 gation is seen in Microgromia socialis, where individuals 

 remain united for a time by their pseudopods, sometimes 



