Arcellina.] the infusoria. 16^ 



Family IX.— ARCELLINA. 



This family contains polygastric animalcules, who 

 possess an alimentary canal, a single opening of the body, 

 are provided with a lorica, and who can change their 

 figure by means of the variable pediform processes with 

 which they are furnished. The lorica, which is univalved, 

 is pitcher or dish-shaped, and the possession of it is the 

 chief feature distinguishing this from the family Amoeba. 

 The body is soft and gelatinous, and in some cases ap- 

 pears to flow as it were from the opening of the lorica. 

 The organs of locomotion are soft variable processes, 

 situated at the anterior part of the body ; they are some- 

 times withdrawn, at others protruded ; sometimes they 

 appear simple, at other times branched; they are 

 neither feet nor antennae, but a peculiar locomotive appa- 

 ratus. In five species, numerous digestive vesicles are 

 seen. No traces of a sensitive system have been disco- 

 vered. The reproductive system is unknown, neither has 

 increase by self-division, the formation of gemmae, or 

 otherwise, been recognized. 



The genera are related to each other as follows : — 



Changeable processes / Lorica spheiical or Uui-like Difflugia. 



radiant, J 

 generally numerous ( Dish or shield-shaped Arcella. 



Changeable processes broad and undi%nded Cyphidium. 



Genus XLI. Difflugia. The diffiuent Animalcules. — 

 This genus is characterized by the creatures having the 

 variable processes, which issue only from the fore part of 



