THE SPONGIDA OR PORIFERA. 355 



surface, they are engulfed within the sarcode substance of the 

 monad's body (see/ and arrows, Fig. 5, Plate XVI.). The food- 

 particles after ingestion are gradually accumulated into spherical 

 agglomerations (r, <r), and then regurgitated through the body 

 under conditions nearly identical with those exhibited by such a 

 higher improvised type as Vorticella. The indigestible residua are 

 eventually liberated from the area limited by the base of the 

 collar, within which they previously gained access." 



Other important characteristics are the presence of two or 

 more contractile vesicles (^, e) situated in the under portion of the 

 monad's body, and the presence of a well marked neucleus {d) 

 or neucleolus. Now, Saville Kent insists that the flagellate 

 collared cells in the Spongida (see Fig. 3 a, Plate XVI., and Fig. 

 2, Plate XV.) correspond, "structurally and functionally, in every 

 detail," with the independent collared Infusoria. " The collar," 

 he says, " in either case presents the same structure and functions, 

 exhibits the same circulatory currents or cyclosis, and acts in a 

 precisely similar manner as a trap for the capture of food. The 

 body contains an identical, centrally-located, spheroidal neucleus 

 or endoplast, and a corresponding, posteriorly located series of 

 rhythmically pulsating contractile vesicles." There are other 

 remarkable points of resemblance. The independent monads are 

 capable of extraordinary changes of form, retracting both collar 

 and flagellum, throwing out sarcodous processes or pseudopodia, 

 and assuming various amoebiform aspects. So it is with collar 

 cells of the Spongida. Saville Kent points out that the dissec- 

 tions of a living Sponge, and examination of the flagellate cells, 

 should be proceeded with quickly, as the cells are apt to soon 

 withdraw collars or flagella, or both, throw out variously shaped 

 sarcodous processes, and take on the most curious shapes (Fig. 3, 

 ^, b, c, d, e,f,g, h, /, Plate XVL). These amoebiform cells may 

 also re-attach themselves to a spiculum of the Sponge, withdraw 

 their pseudopodic extensions, throw out once more collars and 

 flagella, and throw out also a thin bed or investment of sarcodous 

 material. 



Certain genera of the Flagellate Infusoria, as Fhalatisterium 

 and especially Frotospo?igia, are very near to the Spongida as 

 regards their condition of colonisation, as the monads are asso- 



