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 mioronuclei 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 G-ymnostomaceae 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 ^ 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 th& 

 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 ii-regular, 

 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 (Carchesmm) 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 



' Save the Opalinopsidae, which are usually termed " Opaliuidae "; but which 

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

 Flagellates. 



VOL. I ^ 



