of the Cilio-flagellate Infusoria. 275 



it. It would seem, therefore, to be dependent upon the simple 

 cilia around it for the transfer of food to its lips. From the 

 mouth the oesophagus {oe) passes obliquely backwards and toward 

 the dorsal region, at least halfway through the body, and then 

 terminates rather abruptly just before the contractile vesicle, 

 but a little to the right side (fig. 3 a?) of the axial plane. At 

 the mouth it is widest antero-posteriorly, but suddenly narrowing 

 a little, it afterwards gradually lessens its calibre as it extends 

 into the body, and finally ends as just described. The whole 

 track of this channel is much more readily seen than the mouth. 

 The food is taken in such excessively small particles that its 

 entrance into the mouth cannot be detected with any degree of 

 satisfaction ; and a single digestive vacuole (dv) requires from 

 twenty minutes to half an hour to form and fill; and although 

 it may be comparatively quite large, even two-thirds of its fullest 

 capacity, yet so infinitesimally minute are the particles, that 

 even indigo or carmine is not readily seen, although it may be 

 the only kind of food present. Beyond this point, however, 

 these colouring-matters become rapidly visible, so that when a 

 vacuole is fully formed, the indigo or carmine is as conspicuous 

 as in any other Infusorian. These vacuoles are very large, in 

 fact equalling in size the contractile vesicle ; and as they form 

 sometimes pretty far back, they are apt to obscure the latter — 

 without doubt thus causing this vesicle to be mistaken for one 

 of them, since they bear a certain resemblance to it. No anus 

 was detected during these investigations, although the specimens 

 at times were kept well fed. 



The Locomotive Organs. — The most prominent among the cilia 

 is the so-called flagellum (fl). This, however, is not a single 

 filament, as has usually been asserted; but, owing to the manner 

 in which it is used, it very naturally appears to be so. Most 

 frequently its compound nature becomes apparent when the 

 numerous cilia of which it is composed divide into two groups 

 (fig. 7 fl,fl l ), thus simulating a double flagellum*. At other 

 times, after having divided into two groups, they twist about 

 each other in such a way as to resemble a sharply pointed screw, 

 with a long drawn-out double thread. Such is the condition in 

 which this pseudo-flagellum is most frequently seen, and then, 

 with the best magnifying-powers, up to five hundred diameters, 

 its compound nature is not easily recognized. But there are 

 times when the whole group of cilia spreads out into a distinct 

 brush, so that each individual cilium may be seen. The base 

 (fl 1 ) of attachment is in the axial plane of the body, a short dis- 



* Claparede (loc. cit.) speaks of frequently noticing that some of the 

 Ceratiums, &c., appeared to have a double flagellum. Probably they were 

 a group of cilia divided as here described. 



19* 



