INFUSORIA. 



39 



Paramoeciiim (fig. 18) ia a beautiful slipper-shaped little creature, 

 which may be found commonly in stagnant waters or in artificially 

 prepared infusions. The body is nearly quite transparent, and con- 

 sists of three layers — 1, a structureless, 

 transparent, external film or pellicle, 

 called the " cuticle " ; 2, a central mass 

 of soft semi-fluid sarcode which receives 

 the particles of food ; and 3, an intermedi- 

 ate layer of firm and consistent sarcode, 

 which ia called the " cortical layer " 

 (Lat. cortex, bark). The external mem- 

 brane or cuticle is richly covered with 

 minute vibrating haira or cilia, which 

 in this particular type are of approxi- 

 mately equal length, and are arranged 

 in close-set longitudinal rows. In many 

 of the Infusoria, however, the cilia in 

 the neighbourhood of the mouth are 

 much longer than those covering the 

 general surface. The cuticle is also per- 

 forated by the aperture of the mouth, 

 which is continued into a short funnel- 

 shaped gullet (fig. 18, m g). The gullet, 

 however, is not continued into any dis- 

 tinct stomach, but opens directly into 

 the soft semi-fluid sarcode (endoplasm) 

 which constitutes the central mass of 

 the body. The particles of food on 

 passing through the gullet are directly 

 received into the central mass of dif- 

 fluent sarcode, where they undergo a 

 kind of slow circulation or rotation. 

 As in the case of the Amoeba, each par- 

 ticle of food generally carries with it 

 a little water, so that the appearance is 

 nroduced of a number of little clear 



Fig. 18. — ParamcECium, viewed dorsally, and greatly magnified, m Moutli ; m to gr 

 Gullet ; a Anus ; ci/ and cv Tlie contractile vesicles ; I, II, III, Canals proceeding 

 from the anterior contractile vesicle ; n Nucleus ; v Large cilia bounding tlie de- 

 pression ('* vestibule ") leading to tlie mouth. The arrows indicate the course in 

 which the particles of food circulate in the semi-fluid protoplasm of the interior of 

 the body. (After James-Clark.) 



spaces in the central sarcode. These are now called vacuoles, or 

 food-vacuoles ; but they were originally described by Ehrenberg, -the 



