CLASS III. KHIZOPODA. 



THESE are microscopic animals closely allied to 

 the Infusoria, of very simple structure, consisting 

 of little more than a transparent glaire or thin 

 jelly. They have, however, the power of throwing 

 out from various parts of the surface long tenacious 

 threads of the common jelly, which are irregularly 

 connected and branched, and which are completely 

 retractile at the will of the animal. 



Some of these beings are entirely unprotected 

 by any covering, and others are enveloped in a 

 horny case or box, which has several openings for 

 the emission of the processes. Specimens of both 

 of these kinds are common in our fresh waters, 

 constituting the genera Amoeba^ Difflugia, Arcella, 

 &c. Others, however, and these by far the greater 

 number, secrete a calcareous shell, analogous to 

 that of the MOLLUSCA, which is moulded upon the 

 gelatinous body, and is perforated with minute 

 orifices, for the purpose above mentioned. This 

 last character has given to the shell-bearing Rm- 

 ZOPODA the name of FORAMINIFERA. 



In the simplest forms the shell has but a single 

 chamber; in others chamber after chamber is 

 added to the first, each connected with the pre- 

 ceding ones by a tube or aperture, though it is the 

 last only which is inhabited. This addition may 

 be made in a straight or curved line, or in one 

 rolled on itself in a flat or oblique plane, and in 

 one or more series, or in an irregularly crowded 

 manner. 



