93 PROFESSOR O. BiJTSCHLI. 



posterior end until it reaches the hinder third of the body. 

 Biitschli's hypothesis is that this apparatus is nothing but an 

 oesophagus, which, beginning at the anterior Hp-like end of 

 the body, sinks into the body. The ingestion of food has 

 not been watched. Both the dorsal and ventral surfaces are 

 more or less distinctly ribbed longitudinally, but this is 

 sometimes scarcely perceptible. 



The contractile vacuole is in exactly the same position at 

 the base of the flagellum, as in the preceding species. The 

 nucleus lies on the same side of the body, somewhat towards 

 the centre ; it possesses the structure that is usual amongst 

 Flagellata, viz. the vesicular, with a large dark inner 

 body. A considerable number of secretion granules is 

 found in the body protoplasm, in addition to the food ele- 

 ments. A considerable number of observations have been 

 made on these organisms in relation to the process of fission. 

 Individuals which are preparing to undergo this process 

 shoAV the longitudinal banding much better and more clearly 

 than is the case in ordinary specimens, in which there is 

 often no trace of this ribbed appearance, although, as 

 already remarked, it appears very clearly during the fission 

 (fig. 20 b). 



The earliest condition of division which the author has 

 observed shows the flagella for both the young forms in full 

 perfection, close to each other, at the anterior end of the 

 somewhat compressed organism (fig. 20 b). The method of 

 the formation of these flagella was not followed out, but, so 

 far as is known, it does not appear to occur in the way 

 described by Dallinger and Drysdale^ for a very much 

 smaller Flagellate, 0'0085 mm., of Anisonema-like form. The 

 pair of contractile vacuoles for the two offspring are present 

 before the constriction of the body takes place, and this 

 remark should apply also to the mouth apparatus, but on 

 this point observations are wanting. The actual longitu- 

 dinal division of the body of Anisonema occurs in a one- 

 sided way, for the constriction between the flagella begins 

 at the anterior boundary, and gradually pinches through 

 the body backwards, without any constriction occurring 

 from behind (fig. 20 c — f). Finally, the two young off"- 

 spring hang together by their posterior ends only by a 

 delicate thread, which is ultimately broken through. After 

 treatment of one of these dividing organisms with dilute 

 acetic acid the condition of the nucleus is rendered visible. 



> " Further Researches on the Life-history of the Monads," ' Month 

 Micros. Journ.,' 1873, Vol. X, p. 245. 



