vi CILIATA 145 



remains intact. If an Infusorian be divided into small parts, 

 only such as possess a micronucleus and a fragment of the mega- 

 nucleus are capable of survival. We shall see how important a 

 part the micronuclei play in conjugation, a process in which the 

 old meganuclei are completely disorganised and broken up and 

 their debris expelled or digested. 



The mouth of the Gymnostomaceae is habitually closed, 

 opening only for the ingestion of the living Protista that form 

 their prey. It usually opens into a funnel-shaped pharynx, 

 strengthened with a circle of firm longitudinal bars, recalling 

 the mouth of an eel-trap or lobster-pot (" Eeusenapparat " of the 

 Germans) ; and this is sometimes protrusible. In Dysteria the 

 rods are replaced by a complicated arrangement of jaw- or tooth - 

 like thickenings, which are not yet adequately described. We 

 have above noted the strong adoral trichocysts in this group. 



In all other Ciliates l the " mouth " is a permanent depression 

 lined by a prolongation of the pellicle, and containing cilia and 

 one or more undulating membranes, and when adoral membranellae 

 are present, a continuation of these. In some species, such as 

 Pleuronema (Fig. 57), one or two large membranes border the 

 mouth right and left. In Peritrichaceae the first part of the 

 pharynx is distinguished as the " vestibule/'' since it receives the 

 openings of the contractile vacuole or its reservoir and the anus. 

 The pharynx at its lower end (after a course exceptionally long 

 and devious in the Peritrichaceae ; Figs. 51, 60) ends against the 

 soft endosarc, where the food-particles accumulate into a rounded 

 pellet ; this grows by accretion of fresh material until it passes 

 into the endosarc, which closes up behind it with a sort of lurch. 

 Around the pellet liquid is secreted to form the food-vacuole. 

 If the material supplied be coloured and insoluble, like indigo 

 or carmine, the vacuoles may be traced in a sort of irregular, 

 discontinuous circulation through the endosarc until their remains 

 are finally discharged as faeces through the anus. No prettier 

 sight can be watched under the microscope than that of a colony 

 of the social Bell-animalcule (Carchesium) in coloured water all 

 producing food-currents brilliantly shown up by the wild eddies 

 of the pigment granules, and the vivid blue or crimson colour of 



1 Save the Opalinopsidae, which are usually termed "Opalinidae" ; but which 

 cannot retain the latter name on the removal of the genus Opalina to the 

 Flagellates. 



VOL. I L 



