288 CCELHELMINTHES 



strongly bent alimentary canal extends into the ccelom and is bound 

 at its hinder end by a cord, thefuniculus, to the base of the cystid. Gang- 

 lion and nephridia lie between the mouth and anus. The gonads arise 

 from the epithelium of the ccelom, the testes usually on the funiculus, 

 the ovaries on the wall of the cystid. 



Hundreds and thousands of individuals form colonies (fig. 275) in 

 which cystid abuts against cystid. The ccelom of adjacent cystids may 

 be distinct or a wide communication may exist. The colonies grow by 

 budding; in the Gymnokemata a part of a cystid becomes cut off as a 



FIG. 275. -Small colony oiLophopus crystallinus Rafter Kraepelin), with young and old, 

 some extended, others more or less retracted, o, statoblasts. 



daughter cystid in which the polypid alimentary tract and tentacles- 

 arises by new formation; or (Phylactolsemata) the bud anlage of the 

 polypid arises before the first appearance of the cystid. 



Division of labor or polymorphism is common. Besides the animals 

 already described, which are primarily for nourishment, three other indi- 

 viduals may occur, ovicells, vibracularia, and avicularia. All three are 

 cystids which have lost the polypid The ovicells are round capsules which 

 serve as receptacles for the fertilized eggs. The vibracularia (fig. 274, B) 

 are long tactile threads: the avicularia (fig. 274, A) are grasping structures 

 which seize small animals and hold them until decay sets in ; the fragments 

 serve as food for the polypids. The avicularia have the form of a bird's 

 head, the movable lower jaw being a modified operculum. 



Under unfavorable conditions a polypid in a cystid may break down and be 

 lacking for some time until better relations cause its new formation. Besides, 

 in the depopulated cystids, there may appear statoblasts, internal buds en- 

 veloped in a firm envelope which form a resting stage (fig. 275). Each stato- 

 blast is surrounded by a girdle of chambers which by drying become filled with 



