50 MANUAL OF ZOOLOGY. 



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 Amoeba. 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 Foraminifera. A nucleus and contractile vesicle 

 are also present. The long filamentous pseudopodia of Actino- 

 phrys 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 Amcebea may be divided into two sub-orders : i. Am&- 

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

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

 by a carapace. 



CHAPTER III. 

 FORAMINIFERA. 



THE Foraminifera may be defined as Rhizopoda in which the 

 body is protected by a shell, or " test" usually composed of car- 

 bonate of lime; there is no distinct separation of the sarcode oj 

 the body into ectosarc and endosarc, and the nucleus and con- 

 tractile vesicle are both absent. The pseudopodia are long and 

 filamentous, and interlace with one another to form a network. 

 The Foraminifera are specially characterised by the posses- 

 sion of a " test " or external shell, which is usually composed 

 of carbonate of lime, but is often composed of grains of sand 

 or other adventitious solid particles cemented together by 

 animal matter. (If Lieberkiihnia is to be regarded as a 

 Foraminifer, the possession of a test cannot be looked upon as 

 essential, since this animalcule is naked.) The test is usually 

 composed of an aggregation of chambers or " loculi " (fig. 4, c), 

 and its walls are usually pierced by numerous pores or 

 " foramina " through which the pseudopodia are protruded ; 

 the place of these being in some forms supplied by the large 

 size of the terminal, or " oral" aperture of the shell (fig. 4, b). 

 The presence or absence of foramina in the shell-walls is be- 



