82 PllOFESSOR O. BiJTSCHLI. 



been seen to gradually assume an active condition, and 

 then to take on the more elongated form. Sometimes the 

 organisms appear to have such power of change that their 

 outline becomes irregular, and they even exhibit amoeboid 

 movements. The protoplasm of the Hexamiti is very clear 

 and transparent, as in Trepomonas agilis and Pyramimonas 

 descissa. In the first form there are some interesting agree- 

 ments as regards the relations of the contractile vacuoles. 

 There is much difiiculty in determining the exact number of 

 the long flagella, but Biitschli believes that he has been able, 

 from observations onliving specimensas well as on thosekilled 

 by treatment with chromic acid and solution of iodine, to fix 

 the number at eight. Of these eight flagella two spring from 

 the hinder corner, which is either blunt or slightly indented; 

 as Dujardin has observed, these two flagella are drawn along 

 by the general movement, without themselves moving to any 

 great extent. The organisms also attach themselves for a 

 time by this posterior pair of flagella, and rotate rapidly on 

 their axes, as if anchored. In addition to these, three flagella, 

 the active agents in causing motion, arise on each side of 

 the body; they are of very considerable length. The pro- 

 toplasm of the body is in part quite free from granules, and 

 is, therefore, transparent ; in part, however, there are con- 

 siderable numbers of granules of varying size, and of a dark 

 nature ; many Hexamiti also contain a number of long, very 

 dark and shining bodies (fig. 15, h), which sometimes entirely 

 fill up the interior of the organism, occasionally similar 

 bodies, of a dark brown colour, are visible. No investiga- 

 tions into the chemical nature of these bodies has been made, 

 but as they are frequently found swimming freely in the 

 water, which is inhabited by the Hexamiti, there is no doubt 

 that the latter take them in as solid food, although the exact 

 mode is still unknown. A single nucleus has often been clearly 

 observed about the centre of the body (fig. 15 a, n) ; it is of the 

 same nature as in Trepomonas agilis. A contractile vacuole 

 is situated at one side and another at the posterior extremity 

 (fig. 15, a, h). After the contraction the following curious 

 phenomenon occurs during the re-formation. An elongated 

 clear space, filled with fluid, makes its appearance near the 

 spot where the previous vacuole disappeared; this space 

 rapidly becomes round, and is then slowly pushed forwards 

 through the body, it soon turns back until it reaches the spot 

 at which the previous vacuole contracted ; the systole then 

 occurs. Sometimes the new vacuole is produced before the 

 systole of the previous one, but after this has taken place 

 the new one is pushed to the hinder end, where it contracts. 



