Natural History of the Infusoria. 327 



purpose. The contractions which then take place are probably 

 the same that were observed by Ehrenberg. In other respects I 

 have found the form quite unchangeable, and Chlorogonium must 

 consequently be separated from the Astasicea, amongst which it 

 has hitherto been arranged. On the addition of iodine only a 

 few blue granules are to be seen in the fusiform individuals ; 

 the green spheres, on the contrary, which are completely filled 

 with green granules, acquire a deep blue colour with this reagent : 

 if the colouring matter be destroyed by means of concentrated 

 sulphuric acid, the granules are dissolved, and on the addition 

 of iodine a beautiful blue colour is produced. By long keeping 

 the green of the cysts passes to red. The cysts are not to be 

 roused from their torpid state by the production of fermentation. 

 I have, however, observed their revivification under other circum- 

 stances, but my materials are insufficient to enable me to describe 

 the mode of reproduction of the investing membrane and 

 filaments, which would certainly be interesting. The conditions 

 required for the existence of Chlorogonium are apparently quite 

 different from those of Polytoma ; the former did not multiply 

 abundantly in infusions until the latter had passed to the state 

 of repose. 



To show how very different is the mode of division in other 

 Monadina, in which the investing membrane is deficient, we 

 may refer to Chilomonas pa?*amecium,J?thvhg. (p. 30. tab. n. fig.vi.). 

 The form of this animal is subject to considerable variation. It 

 usually presents a longish oval, broader at one end than at the 

 other. At the broader end, a little to one side of the apex, 

 there is a small indentation, in which the two filaments are 

 placed. The interior is principally filled with round granules 

 (as represented by Ehrenberg), which distinctly exhibit the re- 

 actions of starch. In the hinder portion a clear nucleus with a 

 reddish halo may be observed. The oval is but rarely perfect ; 

 it is generally flattened on two sides, and the surfaces thus pro- 

 duced are even somewhat impressed in a longitudinal direction. 

 It is to this impression, I think, that the reddish colour which 

 makes its appearance when the animal is examined lying flat 

 before the observer, is to be ascribed. I could discover no con- 

 tractile space, although a reddish vesicle certainly does always 

 exist in the anterior extremity ; I must, however, leave its con- 

 tractibility an undecided point. Ehrenberg mentions expressly, 

 that Chilomonas paramecium never could be made to take in 

 coloured nourishment, nor have I been able to observe this any 

 more than with Polytoma. 



Whatever number of these animals may be observed, no trace 

 of division will ever be remarked in them. Very rarely we may 

 see two individuals adhering by their middle, evidently produced 

 by a longitudinal division. We shall endeavour to explain this. 



