26 INVERTEBRATE AXIMALS. 



pulling the body in the same direction. In the same way, -when 

 any minute pai-ticle of food, such as a microscopic plant, comes 

 within its reach, the Amceha wraps «, pseudopodium round it, and 

 then withdrawing the 2iseudopodium, lodges the nutrient particle 

 securely in the substance of the body. It follows from this that 

 the Anirehii has no permanent mouth — no aperture, that is, which 

 is especially employed in the admission of food. Any part of the 

 surface can be pushed out into a pseudopodium, and therefore a!;y 



Fig. 0. — Aiiicebea. A, Small Ama'hw developed in organic infusions, greatly niagnilied. 

 B, Amaha princeps: n Nnclcus; c Contractile vesicle; v Region of the body where 

 indigestiljle matters are thrust out. 



])art of the surface can be extemporised into a mouth. The process 

 of taking food, in fact, in the An'ia'lxi, has been aptly com])ared to 

 thi'usting a stone or any other solid body into a lump of doiigh. 

 The central jiortion of the body of the animal is softer and more 

 fluid than the outer layers, and the particles of food, on reaching 

 this jioint, undergo a sort of digestion, and are subjected to a species 

 of movement or rotation in the interior of the animal. Each particle 

 of food, in the jjrocess of being taken into the body, usually cai'ries 

 with it a little ilrop of water ; and in this way a number of clear 

 spiices are finnied, which are usually quite round, and look like 

 distinct ca^'ities. These spaces are called "vacuoles"; but they are 

 not di.stinct organs of aii\' kind, though formerlj' regarded as distinct 

 stom.iclis. Having undergone digestion, any portions of food which 

 may be in<Iigestil>le or insoluble are simply thrust out again thi'ough 

 the walls of the body. This ajspears to be effected at one particular 

 ]i.iit of the body; but there is no permanent aperture for the pur- 

 ]iose. There are no distinct vessels which serve to convey the 

 nutritive fluid derived from the digestion ; but there does appear 

 to be a rudimentary organ by which this fluid is driven throuo-h 



