74 IJsFUSOEIA. 



learns to recognise the appearance presented by 

 the aggregated colonies of Vorticella or Epistylis. 

 There are no true fossil Infusoria, the organisms 

 usually designated by this name being either Fo- 

 raminifera, Polycystina, or Diatoniacece. 



13. ;Rfc^octilM«'s?. — Certain of the marine Infu- 

 soviet are phosphorescent, contributing, along with 

 other animals, to impart a luminous appearance 

 to the sea-water wherein they abound. But this 

 remarkable property is possessed in a much more 

 eminent degree by JS'octiluca, an organism whose 



Fii). 16. 



NOCTILUCA MILIARIS. 



true position in the animal kingdom has long 

 been much misunderstood. The simplicity of its 

 organisation shows it to belong to the Protozoa ; 

 and, since it is provided with a distinct mouth, it 

 ought probably to be regarded as an aberrant 

 member of the gi'oup Infusoria. Its structure has 

 been of late years investigated by Quatrefages, and 

 Krohn, and still more recently by Mr. Huxley. 

 In form it is nearly globular, presenting on one 

 side a * hilus,' or groove, from the anterior extra- 



