Development of the hifusoria. 251 



the green-coloured infusoria to swallow colouring matter. In 

 the En^lena viridis, Ehr. {Cercaria viridis, Miill), I recog- 

 nised distinctly the red eyes, but could never detect any other 

 red point, however long it was left in the solution of carmine. 

 The remarkable Vorticella versatilis or Ophrydium versat. Ehr. 

 could never either l>e induced to take the colouring matter. I 

 found this species in great numbers towards the end of October, 

 forming gelatinous balls of an inch and a half in diameter; 

 they were best adapted for experiment, when their size was about 

 yV"- This wonderful animal is of a beautiful green colour, 

 paler, and more transparent near the edges: their interior con- 

 sists of a granular matter, or of small round vesicles (.?) 



IV. On the Change of Form, and the Successions of Inju&oria in 



Infusions, ,, 



It appears very probable, from the observations of Ehrenberg, 

 that the genus Monas, and several of the allied genera, are not 

 distinct animal forms, but merely the young state of the Kolpo- 

 da^ Paramacia, &c., which are unable to reach maturity with- 

 out a division like the Rhizomorpha and Byssus among the 

 Fungi. This idea has been subsequently adopted by Dr Esch- 

 weiler. I have myself no continued observations on the primi- 

 tive generation of the Infusoria, but for several summers the 

 appearance mentioned by Eschweiler * has appeared to me very 

 remarkable. I have seen monads and other small infusoria ap- 

 pear in infusions which disappeared in a few days, and gave 

 place to other genera. Thus the water above mentioned as 

 containing the Hydatina, on the seoond day after being taken 

 from the pool, formed a green crust on its surface, particularly 

 near the margin of the glass in which it was kept. When I 

 examined this green mass with the microscope on the 23d Octo- 

 ber, it swarmed with the Euglena viridis and Enchelys pidvis- 

 cuius, which swam about with much activity. Some of the first 

 species were seen in the act of expiring, and others quite dead. 

 During this curious phenomenon the elongated form of the ani- 

 mals was changed into a globular. They died in whole masses, 

 particularly near the margin of the vessel ; the green crust then 

 forming the so-called Priestley's matter, although it may arise 



• Isis. 1831, Heft. iv. p. 403. 



