46 MANUAL OF ZOOLOGY. 



CHAPTER III. 



FORAMISIFERA. 



THE Foraminifera may be defined as Rhizopoda in wliicli the 

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

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

 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 net-work. 



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 sometimes membranous. (If 

 Lieberktihniaia to be regarded as SbForaminifer, 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,' 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 sup- 

 plied by the large size of the terminal, or ' oral,'' aperture of 

 the shell. 



As regards the soft parts of the Foraminifera, the body is 

 composed of extensile and contractile sarcode usually reddish 

 or yellowish in colour which not only fills the interior of the 

 shell, but generally invests its outer surface also with a thin 

 film, from which the pseudopodia are emitted. The sarcode is 

 not differentiated into a distinct ectosarc and endosarc, and is 

 devoid of a nucleus and contractile vesicle, and, indeed, of any 

 organs or specialised parts of any kind. From this uniformity 

 in its composition there seems some reason to conclude that 

 the Foraminifera in spite of the complexity and mathematical 

 regularity of many of their shells should be looked upon as 

 the lowest forms of the Rhizopoda, or even of the Protozoa. 



The pseudopodia in all the Foraminifera are filamentous 

 and protrusible to a great length, and they possess the 

 singular property of uniting together in various directions so 

 as to form a kind of net- work, like an ' animated spider's- 

 web.' (Hence the name Reticidaria applied to the order by 

 Dr. Carpenter.) This property, however, is not peculiar to 

 members of this order, but is seen also in Actinophrys and in 

 the Thalassicollida, though to a less extent. Further, through- 

 out the entire net- work formed by the inosculating pseudo- 



