OF ANIMALCULES. 121 



GENUS XIII. 

 TRICHODA. 



DIAPHANOUS, PARTIALLY CILIATED ANIMALCULES. 



This genus is very extensive, and contains several 

 species of the Rotatoria, with a complete alimentary 

 canal, as well as many of the polygastrica. Some of them 

 are of sufficient size to be visible to unassisted vision. 



{A.) Polygastrica, [a) nuda, 



230. Trichoda grandinella (Trichodina grand. E) 

 The hoar 'frost Trichoda. — This is a minute polygastric ani- 

 malcule, with a single circle of cilia: it resembles the 

 Vorticella convallaria, but has no foot-stalk or pedicle. 

 The best method of observing the cilia is by employing 

 an intense illumination, and reducing the quantity of light 

 by diaphragms under the stage*, till the maximum of dis- 

 tinctness is obtained. I have always found that the ad- 

 dition of a little colouring matter, finely divided, lessens 

 the difficulty of discovering them. Figure 135 is a mag- 

 nified sketch of this species. Size, 1-llOOth of an inch. 

 Found in vegetable infusions. 



231. Trichoda cometa. The comet Trichoda. — This 



* See " Microscopic Cabinet," page 128. 

 K 



^M. 



