THE INFUSORIA. 



97 



under some circumstances, shoot out into long filaments, 

 and have been termed trichocysts. In P. bursaria, minute 



Fig. 10.— Paramecium bursaria (after Stein).— ^1, the animal viewed from the dorsal 

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

 ters taken in as food ; e, chlorophyl granules. 



B,the animal viewed from the ventral side: a, depression leading to b mouth- 

 c, gullet ; d, endoplast ; d\ endoplastule ; e, central protoplasm. In both these 

 figures the arrows indicate the direction of the circulation. 



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

 ing ; c c\ 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 Algse. In Balanti- 

 dium, JVyctotherus, Spirostomum, 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 Ciliata, the endosarc appears to be almost fluid. 

 The food, which is driven into the mouth and down the 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 

 Ralantidium ; in Paramoecium, the tract through which the 

 food- vacuoles move is more definitely limited, 1 while in JSTyc- 



m » In Parametrium bursaria Cohn observed that the circulation was completed 

 in H to 2 minutes, which gives a rate of rotation of ,&, to „$,« of an inch in 

 a second. 



5 



