FLAGELLATE INFUSORIA AND ALLIED ORGANISMS. 83 



This phenomenon of the vacuole presents considerable like- 

 ness with the appearances observed in Trepomonas. The 

 length of the Hexamiti was about 0*01 to 0'02 mm. Fission 

 alone of the processes of reproduction has been observed, and 

 that not in detail. 



Pyramimonas, Schmarda ('Neue Formen von Infusioren : 

 Denkschrift der k. Acad. d. W. zu Wien. M. Naturwis- 

 sensch. Classe/ Bd. i, 1850 ; * Abhandl. von Nichtmitglie- 

 dern,' p. 9, pi. iii, fig. 1). 



Tetramitus, Perty {' Zur Kenntniss kleinster Lebens- 

 formen,' p. 170). 



Pyramimonas descissa, Perty (op. cit., p. 170, pi. xiv, 



fig- ^}' . . 



This is, again, an exceedingly interesting species, of which 



two distinct forms appear to be known, the one described 

 here, the other, Tetramitus rostratus, of Perty,^ which has 

 been figured by Fresenius,^ without further description. 



Pyramimonas descissa is a small organism which Biitschli 

 has only once found in any quantity ; it occurred in foul 

 pond water. The appearance of the organism is elongated, 

 and is rightly described by Perty as being cone-shaped 

 (PI. VI, fig. 16, a), since the hinder end is the more pointed, 

 although this is not regular, as this end is sometimes quite 

 round, as fig. 16, b. The anterior extremity is exceed- 

 ingly typical, for it is sharply oblique, so much so, indeed, 

 that the oblique surface is slightly inclined towards the axis 

 of the organism so as to embrace the entire anterior extremity 

 of the body. The oblique surface is concave. Anteriorly 

 are four flagella, of which the posterior is the shortest, 

 whilst the most anterior is the longest. By means of these 

 flagella the organism rotates rapidly and regularly, and con- 

 sequently its examination is attended with diificulty. The 

 very clear protoplasm of the body contains numerous dark 

 granules, which give the impression of being food particles, 

 since they are in many cases enclosed in large vacuoles. 

 That such is actually the case is proved by the fact of 

 such particles having been seen to be thrust out of 

 the body. The simple contractile vacuole lies at the 

 hinder end of the body (fig. 16, a, and b, u) ; it contracts 

 rapidly and suddenly. Two small and fresh vacuoles appear 

 before the systole of the previous vacuole begins ; after this 



^ Op. cit., pi. xiv, fig. 4. 

 * PI. X, fig. 34, 35. 



