INFUSORIAL ANIMALCULES. 11 



Cryptomonas glauca, Cryptoglena conica, Pandorina 

 morum, Gonium pectorale, Chlamidomonas pulv., Volvox 

 glob., Astasia and Euglena sang., when young ; Euglena 

 viridis, Chlorogonium enchylis, and Ophrydium versa- 

 tile : yellow from the Astasia flavicans ; a milky tint from 

 the Polytoma uvella, and Ophryoglena atra, when they are 

 numerous. A bright orange coating is given by Stentor 

 aureus. 



The rapid and mysterious transition of colour which is 

 observable in lakes, and which has often created an alarm 

 in the timid minds of the superstitious inhabitants on 

 their borders, the microscope has shewn to arise from 

 certain changes in the condition of Infusoria. Thus, a 

 lake of clear transparent water will assume a green colour 

 in the course of a day ; nay, more, it will become coloured 

 and turbid in the middle of the day, when the sun brings 

 these creatures to the surface, and rapidly develops them, 

 or causes their dead bodies to ascend, whilst in the morn- 

 ing and evening it will again be clear. 



The phosphorescence of the sea appears to be occa- 

 sioned, in many instances, by the presence of animalcules, 

 which, although individually imperceptible, often render 

 luminous many miles of water by the immensity of their 

 numbers. 



In the same manner, large arborescent figures, resem- 

 bling Fuci and Algae, are formed by the Micromega; and 

 masses of great extent by the Epistylis and Schizonema. 



The Bacillaria, or their shell-like coverings (Loricae) 

 are often spread over many miles of the earth's surface, 

 descending also to a considerable thickness, the remains 

 of which, when they become indurated and mixed with 



