FLAGELLATE IKFUSORIA AND ALLIED ORGANISMS. 91 



wall of which it is limited. The arched form extends round 

 to the anterior wall, and then disappears at the point of 

 insertion of the posterior flagellum. This flagellura arises 

 somewhat to the left of the middle line, like the cytostome 

 (cell mouth), and runs along the inner side of the arch in a 

 curve to the anterior extremity, round the cytostome, and 

 backwards along the right side of the ventral surface. 



Somewhat behind the point of insertion of the posterior 

 flagellum, and on the left side, is the contractile vacuole 

 (fig. 19 a, v). The mouth apparatus is seen on the inside of 

 the portion bounded by the anterior curved part of the pos- 

 terior flagellum as a tube-like structure, which does not 

 extend very far back. The nucleus is seen without difficulty, 

 as an oval tolerably large body, at the posterior end of the 

 organism on the right wall of the body. It differs somewhat 

 from the nuclei of the Flagellata which have yet been de- 

 scribed, approaching more nearly to the nucleus of the 

 Ciliata, as it exhibits granular bodies as dark as the sur- 

 rounding protoplasm. In the protoplasm itself are seen a 

 greater or less number of secreted granules, as in Astasia, 

 which are chiefly aggregated at the posterior end of the body. 

 Nothing has been observed by the author in relation to the 

 reproduction, although multiplication undoubtedly proceeds 

 by longitudinal fission. 



Anisonema sulcatum, Dujardin ('Hist. Nat. des Infu- 

 soires,' Paris, 1841, p. 345, pi. iv, fig. 28). 



Bodo (?) grandis, Ehrenberg. 



Anisonema sulcatum, Perty (' Zur kenntniss kleinster 

 Lebensformen,' p. 164). 



These organisms are tolerably common, measuring 0*02 

 mm., and being of a distinctly oval form (fig. 20 a) ; they are 

 not quite so much flattened as is Anisojiema acinus. The 

 peculiar flattened ventral surface, which was described in 

 the previous form, is here wanting. The posterior flagellum 

 runs directly backwards without describing the peculiar curve 

 at the anterior end. The anterior small flagellum which 

 causes motion arises usually from a distinct, but sometimes 

 from a somewhat obscure, notch at the anterior end, some- 

 what to the left of the middle line. The long posterior 

 flagellum is inserted a short distance behind upon the ventral 

 surface, at exactly the same point as in the preceding species. 

 This species attains to nothing like the size of the preceding. 

 The mouth apparatus, commencing at the most anterior point 

 of the body, runs backwards exactly in the middle line; it is 

 distinctly tube-like, becoming gradually smaller towards the 



