230 Infusorial Circuit of Generations. 



or displaying a girdle of cilia round the rear part of the body, it 

 immediately represents the free-roving Vorticella in full equipment. 



Its subsequent " encystment " into a spherical cyst densely 

 covered with short prieJdes (somewhat hke the rim of a Heliopelta) 

 and containing entrail-hke designs, is well known.* Also, that it 

 eventually bursts — occasionally, at least — and disgorges a peculiar 

 sort of '?ra/er-shaped, elliptical (not ellipsoidal !) cells, or nuclei, 

 whose ulterior fate and abode, however, hitherto remained unknown. 



The fact is, that they rise to the surface, where, on account of 

 their shape, they inhere, as an almost imperceptible pellicle or 

 stratum, which to the microscopic observer is the instantaneous 

 index of the precise focality of the surface. 



In this state, when no food is supplied, they long remain unal- 

 tered. When meat, bread, or other nutritive matter is added, how- 

 ever, they develop (particularly where the absence of hght prevents 

 the confervaceous or green, chlorophylline growths from becoming 

 paramount) into the smallest Vorticellse. The centre of the wafer- 

 shaped disk, inherent in the denser surface of the water, protrudes 

 downward into a little clear knoll or navel, which soon begins to 

 jerTi, representing as it were a pin-head of toVo line diameter on a 

 little thread or coiled stalk ; and, as the whole increases in size, it 

 now constitutes the well-known spirally peduncidate Vorticella; 

 pyriform bell-shaped, somewhat pitcher-mouthed, with cilia around 

 the orifice and a clear granular nucleus or " germinal speck " inside. 



The multiplication of the pedunculate Vorticelte, by fission, 

 lengthwise, and by budding-out, sideways, at the rear end, is sufii- 

 ciently known. As the bud tears loose, there is yet no oral aper- 

 ture visible. There is, however, a girdle of cilia at the rear, where- 

 with it performs an undulatory vibration, until it tears loose by 

 spinning round; and after irregularly prancing about, and rebound- 

 ing at headlong speed, within a few minutes it " settles " upon 

 some suitable sui-face, with the ciliated rear end ; and spinning out 

 a podelmm, or peduncle, often within a quarter of an hour, the 

 rear cilia get apphed downward to the body and disappear ; while 

 after a little time a fuUy ciliated mouth now opens in front. 



As for its retrograde multiplications, when a Vorticella gets 

 " sick," for want of au' or food (as when kept between glass-plates 

 held apart and glued round about, or cemented, to prevent evapora- 

 tion), the body contracts to a perfect globe, with a big germinal 

 point, " eye," or nucleus in the middle ; the throat contracted, and 

 the lifeless cilia standing around hke the limb of a rose-calyx. The 

 germinal speck, ogle, or nucleus soon becomes immensely bloated, 

 protruding out of the crown or ciliate aperture like a dim, hazy 

 balloon, and then being either suddenly or gradually exploded, its 

 almost invisible granular contents settle around and increase into a 

 * lu fig. 215, Carp. ' Micr.,' p. 446, the short prickles are omitted, B to E. 



