112 DESCRIPTION OF [Pohjgastrica. 



toglena. Form depressed, elliptical and emarginate ante- 

 riorly; colour blueish-green ; motion quick. Found amongst 

 conferva. Size 1- 6000th. 



Genus XV. TRACHEL.OMON&S. The Monad with the 

 trunk. This genus comprehends those loricated ani- 

 malcules of the family Cryptomonadina which are possessed 

 of the visual organ, and of a closed lorica, of a box-like 

 shape, elongated or spherical, but without the projecting 

 neck. They are furnished with a long single filiform pro- 

 boscis or seta, for the purposes heretofore described, and 

 in two species, T. nigricans, and T. volvocina, very 

 minute transparent vesicles have been discerned, which are 

 most probably their digestive sacs. In the species T. 

 cylindrica egg-like granules are visible. Two species are 

 green, and one blackish -brown. It is most probable that 

 those highly interesting animalcules which enter so abun- 

 dantly into the silicified substances in certain chalk forma- 

 tions belong to this genus. 



67. TRACHELOMONAS nigricans. The blackish Trache- 

 lomonas. Form oval, approaching to globular ; colour 

 rarely green, mostly of a reddish or blackish-brown. Eye 

 brown. Size l-l700th. 



68. TRACHELOMONAS volvocina. The revolving Tra- 

 chelomonas. Form spherical ; colour mostly green, some- 

 times of a brownish hue, but easily distinguished by a red 

 ring on the circumference of the body; vesicles maybe 

 observed within it, which are most probably the digestive 

 sacs, between which a very fine granulated substance is 

 situated, which occasions the colour of the body. It is 

 furnished with a delicate flagelliform proboscis for purvey- 

 ing and locomotion. The red circle, so remarkable a feature 



