THE INFUSORIA. 



97 



under some circumstances, shoot out into loni^ filaments, 

 and iiave been termed trlchocysts. In P. hursaria, minute 





••'^«lr- 



'"'Mw 



■'^«M#' 



Fig. 10.— Paramecium bursnria (after Stein).— vl, the animal viewed from the dorsal 

 side : a, cortical layer of the body ; b, endoplast ; c, contractile space ; d rf', mat- 

 ters taken in as food ; e, chlorophyl grannies. 



5, the animal viewed from the ventral side: a, depression leading to 5, mouth ; 

 <?, gullet ; d, eudoplast; rZ', endoplastule ; e. central protoplasm. In both these 

 figures the arrows indicate the direction of the circulation. 



C, Parammcium dividing trausversly : a a', contractile spaces ; b b, endoplast divid- 

 ing ; cc\ endoplastules. 



green granules of chlorophyl are dispersed through this layer, 

 and Cohn demonstrated, in 1851, that these yield the same 

 reactions as the chlorophyl grains of the Algae. In Balanti- 

 dium^ Nyctotherus^ Spirostomurn ^ and many others, the cor- 

 tical layer is divided by linear markings into bands, which 

 there is reason to believe are rudimentary muscular fibres. 



In many Gillata^ the endosarc appears to be almost fluid. 

 The food, which is driven into the mouth and down tlie oesoph- 

 agus by the constant action of the cilia, accumulates at the 

 bottom of the oesophagus ; and then, with the water which 

 surrounds it, is passed, at intervals, with a sort of jerk, into 

 the endosarc, where it lies close to the end of the oesophagus, 

 as a food-vacuole, for a short time. But it soon begins to 

 move, and, along with other such vacuoles formed before and 

 after it, circulates in a definite course up one side of the body 

 and down the other, between the cortical layer and the endo- 

 plast. This movement is particularly free and unrestricted in 

 Balantidiuin ; in Pararaceckim^ the tract through which the 

 food- vacuoles move is more definitely limited,* while in N^yc- 



^ Tn Paramacium hursaria Colin observed that the circulation was completed 

 in U to 2 minutes, which gives a rate of rotation of boVs to r^soij of an inch in 

 a second. 



