114 



MANUAL OF ZOOLOGY 



SECT. 



coloured gonads, tentacles, or radial canals. In many 

 cases the umbrella, oral arms, etc., are highly coloured, and 

 some species are phosphorescent. They are all carnivorous, 



i.r. 



frr.t 



FIG. 51. Tessera princeps. A, external view; B, vertical section ; g.f. gastric 

 filament ; gon, gonad ; i.r. t. tentacle ; ntnb. manubrium ; inth. mouth ; pr. t. 

 tentacle : st. stomach ; tn. taeniole or gastric ridge. (After Haeckel.) 



and, although mostly living on smaller organisms, are able, 

 in the case of the larger species, to capture and digest 

 crustaceans and fishes of considerable size. 



