52 



MANUAL OF ZOOLOGY. 



that is to say, with the closed end of the carapace elevated 

 above the surface on which it is moving. In Arcella there is a 

 discoid or basin-shaped carapace, secreted by the animal itself, 

 and likewise possessing but a single pseudopodial aperture, 

 placed in this case on the flat surface of the body. 



In Pamphagus there is no carapace, but the pseudopodia 

 are nevertheless protrusible from one extremity only of the 

 body, the remainder of the surface appearing to be of too 

 resistant a consistence to allow of this. The common sun- 

 animalcule {Actinophrys sol) is another well-known Rhizopod 



Fig. 3. — Actino^hrys sol: showing the radiating pseudopodia. 

 One specimen ha^swaliowed a Diatom. 



which is usually placed in this order (fig. 3). It consists of 

 a spherical mass of sarcode, about 1-1300 of an inch in dia- 

 meter, and usually covered with long, radiating, filamentous 

 pseudopodia, which are much less mobile than in the case of 

 the Atnceba. The division of the substance of the body into 

 ectosarc and endosarc is tolerably evident, and the latter 

 contains numerous granules and vacuoles. The pseudopodia 

 are derived from the ectosarc alone, the endosarc not passing 

 into them, and they exhibit a circulation of granules along their 

 edges, though this is not nearly so marked a feature as in the 

 case of the Foraviiniferq. A nucleus and contractile vesicle 

 are also present. The long filamentous pseudopodia of Actino- 

 fhrys make a decided approach to the Foraminifera, and for 

 this reason the sun-animalcule is sometimes placed with the 

 latter in a single order. 



The Ammbea may be divided into two sub-orders : i. Amce- 

 Una, including those forms which have the body naked ; and 

 2. Arcellina, comprising those in which the body is protected 

 by a carapace. 



