PROTOZOA INFUSORIA. 1 45 



Paramoccium. There is an outer cuticlo, a cortical 

 layer, and a central mass of sarcode. The cortical layer 

 contains a contractile vesicle and a nucleus. 



The mouth is situated near the edge of the disc, the 

 fringe of cilia being continued into the oesophagus. The 

 particles of food brought by the cilia, as well as the entire 

 contents of the body, perform a slow rotatory movement 

 through the interior. Indigestible particles are ejected 

 through an anal opening, situated near the mouth. 



212. Development. Reproduction in Yorticella is 

 effected by fission, gemmation, and encystation. The 

 first of these modes is thus described by Gosse : 



" One of the full grown bells begins to alter its form, 

 becoming first globular, then a flattened sphere ; presently 

 a slight notch or depression is observed in the upper part 

 of the outlilie, and it soon becomes apparent that this 

 depression is a constriction extending all round, which 

 gradually becomes deeper and more marked. As the two 

 divisions become more separate, each assumes an oval 

 form, united at length to its fellow only at the base. At 

 this time the motion of the cilia is plainly visible, form- 

 ing a circle in each within the body, near the summit. 

 As the process goes on, the connection between the two 

 is reduced to a mere point, and they become capable of 

 separate motion, so far as to diverge and look in opposite 

 directions ; the point of union being the common stem. 

 At this stage we may observe that the bell which is des- 

 tined to remain is open at the top, within which the 

 ciliary waves are chasing each other in continuous wheels, 

 the other bell being closed at the summit. 



" But on the latter, which is ultimately to be thrown 

 off, a new and highly interesting phenomenon appears. 

 The cilia, which before the division had played around 

 the mouth, have become obliterated, probably by absorption; 

 the orifice at that extremity has closed up permanently, 

 for this is to be the base of the new animal ; and a new 

 bell-mouth and a new wheel of cilia are to be formed at 

 the opposite end, which at present remains attached to 

 15 E. K 



