6 PARAMCECIUM. 



b) The buccal groove running from the rounded end obliquely 



or spirally .back for about two-thirds the length of the body. 



c) The buccal groove ends in a funnel-shaped pocket, the gullet, 



leading into the interior protoplasm. This pocket is usually 

 hard to distinguish. 



d) A dorsal and a ventral surface, determined by the position of 



the buccal groove which occupies the latter. 



e) An inner, semi-fluid and more granular portion of the body pro- 



toplasm, the endosarc or medulla, a firmer outer layer, the 

 ectosarc or cortex, and a thin cuticle closely applied to the 

 latter. This differentiation may not be readily observed unless the 

 student has good typical specimens. 



f) The cilia, hair-like projections of the ectosarc through minute 



perforations in the cuticle. Note that they are of about equal 

 length and are distributed pretty evenly over the surface of 

 the body and down the buccal groove. They function as organs 

 of locomotion and also induce food-bearing currents of water. 



g) The contractile vacuoles, two clear globular bodies near the 



respective ends of the body. Note their gradual increase in size 

 and sudden collapse. How frequently does this action repeat 

 itself. These vacuoles are organs of excretion, being accumula- 

 tions of water and waste material resulting from metabolism which 

 is periodically squeezed out of the body by the highly contractile 

 surrounding protoplasm. 



h) Food vacuoles, particles of ingested food enclosed in a globule of 

 water which is thought to contain some digestive ferment. The 

 food particles are swept down into the gullet by the action of the 

 cilia, and, accumulating in pellets or balls, pass into the interior 

 protoplasm. Portions of indigestible matter are forced out 

 through the body wall at a temporary anal spot below the interior 

 end of the gullet. The feeding process may sometimes be ob- 

 served if a little powdered carmine be added to the drop of water 

 containing the Paramcecia. 



i) The trichocysts. These are little oval sacks lying side by side 

 in the ectosarc giving it a striated or granular appearance. They 



