FLAGELLATE INFUSORIA AND ALLIED ORGANISMS. 65 



(fig. 1 c), to the posterior end, where it ultimately becomes so 

 entirely surrounded that it no longer projects sac-like beyond 

 the body. After a time such particles appear to lose the 

 vacuole by which they were surrounded, and numbers are 

 found lying free in the protoplasm. Occasionally, also, 

 vacuoles containing no food materials are carried backwards. 

 It thus seems as if the vacuoles were formed at definite 

 intervals, and were pushed back without the ingestion of 

 food acting as a necessary stimulus. The vacuoles may also 

 be formed directly on the ingestion of food, although one is 

 usually readily prepared for such an event in the liplike pro- 

 minence. Clark supposed that there was a cytostome or cell 

 mouth between the base of the flagellum and the lip, usually 

 kept closed, which allowed the lip to play a part in the swal- 

 lowing of food. The process of the rejection of food remnants 

 has been observed by Biitschli in a stalked form of moderate 

 size ; the materials to be extruded were surrounded by large 

 irregular vacuoles formed from time to time within the body; 

 these vacuoles were moved to the side on which was the lip, 

 and stood out hernial like from it, when they either emptied 

 their contents, or, still retaining them, were pinched off from 

 the body. 



A single rapidly contracting vacuole was constantly present 

 on the side opposite the lip. A vesicular nucleus with clear 

 border and distinct nucleoli was frequently visible in the 

 anterior part of the body, not far behind the base of the 

 flagellum. 



Of the phenomena of reproduction^ Biitschli only suc- 

 ceeded in observing the frequent divisions, which are executed 

 in a way which seems to be general in the small proportion 

 of Flagellata which have as yet been examined in regard 

 to this point (Plate vi, fig. 2). In the individual which is 

 about to divide a second flagellum makes its appearance. 

 Thus instead of the primitively simple flagellum, two are 

 formed. The shape of the organism, however, is not 

 noticeably changed, except that it appears slightly more 

 globular, and the lip prominence seems to pass away. The 

 further process of division can be followed in fig. 2, a to e. 

 The body of the organism is first constricted and then 

 divided between the separated flagella. The pinched-off 

 parts then gradually draw away from each other for a con- 

 siderable distance, till the two daughter oi-ganisms are only 

 united by a very delicate thread, which ultimately breaks, 

 and the two products of the division separate from each other. 

 The mode in which the multiplication of tb.e flagella takes 

 place is not determined. The entire process of division 



VOL. XIX. NEW SER. B 



