o CILIATE PROTOZOA 



course in the bodv, passing througli stages similar to those m 

 rara,ma,.m. The "faeces are discharged into the vestibule by an 

 anus, Nvliich in some species is a permanent openmg through the 

 ectoplasm. 



REPRODUCTION 



The reproduction of Vorticella takes place by binary fission, 

 which is of two kinds— ordinary fission, and that which forms 

 conjugants. In ordinary fission, the rim closes in over the disc, 

 the body becomes shorter and wider, and the meganucleus 

 contracts and lies across the body, which then divides into two, 

 the plane of fission being in line with the stalk. The nuclei behave 

 as in Paramecium. One of the daughters remains upon the stalk ; 

 the other grows a circlet of ciha in the hinder region, at the level 

 at which the ectoplasm thickens, breaks off, and swims away by 

 means of its cilia, to settle down elsewhere by the end which was 

 attached to the stalk of the parent. It grows a new stalk for itself. 

 In this form of reproduction the offspring are equal in bulk. In 

 the fission which forms conjugants the parent gives rise to one 

 large individual and one or more of a smaller size. The small 

 individuals may arise by unequal binary fission, sometimes called 

 budding, or by equal fission, followed by division of one product 

 into four by repeated fission. ^ The small individuals, by which- 

 ever method they are formed, resemble the free product of 

 ordinary fission in aU but size. 



CONJUGATION 



The small individuals thus formed swim away, and each 

 attaches itself by its hinder end to the lower part of the body of 

 one of the stalked individuals. Most of the organs of the small 

 individual now disappear, and the ectoplasm between the two 

 conjugants is absorbed into their endoplasm, which becomes 

 continuous. The meganucleus in each begins to break up and 

 disappear. Meanwhile the micron ucleus of the small conjugant 

 has divided into two. Now the micronuclei of both conjugants 

 divide twice, so that the larger contains four and the smaller 



' The various kinds of fission of Atnceba, Vorticella, and animals related to them 

 (i*rotozoa, p. 78) may be classed as : (i) equal binary fission (p. 34), (2) budding, 

 '3) repeated fission (p. jii), {4) multiple fission (p. 35). 



