Arceliina.] THE INFUSORIA. 167 



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 times withdrawn, at others protruded; sometimes they 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 l Lorica spherical or tun-like Difflugia. 



radiant, 

 generally numerous ( Dish or shield-shaped Arcella. 



Changeable processes broad and undivided Cyphidium. 



Genus XLI. DIFFLUGIA. The diffluent Animalcules. 

 This genus is characterized by the creatures having the 

 variable processes, which issue only from the fore part of 



