26 



IXVERTF.BRATE ANIMALS. 



jiulliiig the body in the same direction. In the s.ime way, when 

 any minute particle of food, such as a niicrosco])ic j)lant, comes 

 witliin its reacli, tlie Anifehu wraps a ])seiido]iodiuni rcnuid it, and 

 then witlidrawing the ])seii(hi]>odiuni, lodges the nutiient particle 

 securely in the su))stance of the body. It follows from this that 

 the Ama;'>a has mi permanent jnonth — no aperture, that is, which 

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

 surface can be jiusheil out into a pseudopudium, and therefore any 



Fig. 0. — Aiiin-bca. A, Siiiall Ama-l<n: deviilnjierl in nrj^^aliic infusiuii.s, greatly luagiiilied. 

 B, Jyna-ha princp^: 'n, NuciLtus ; c Contractile, vehicle ; v Region of the Ijoely wlier* 

 iridige.stiblc iiiatter.s are thrust out. 



jiart of the surface can lie extemporised into a mouth. The process 

 of taking food, in fact, in the Aiinehu, has been aptly compared to 

 thrusting a stone or any other solid body into a lump of dotig'h. 

 The centnd jiortion of tVie body of the animal is softer and more 

 fluid than the outei' Layers, and the particles of food, on reaching 

 this point, undergo a stirt "f digestion, and are subjected to a species 

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

 of food, in the [ii'ocess of being taken into the body, usually carries 

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

 spaces are formed, which are u.suallv quite round, and look like 

 (li.stinct cavities. The.se sjiaces ;ii-e called " vacuoles "; but they are 

 nut distinct organs nf any kind, thcjugh formerly regarded as di.stinct 

 stomachs. Having undergone digestion, any portions of food which 

 may be indigestible or insoluble are simply thrust out again through 

 the walls of the body. This ajijiears to Ije effecteil at one particular 

 jiart of the body; but there is no permanent a,perture for the pur- 

 pose. There are no di.stinct vesscds which serve to convey the 

 mitritive fluid derived from the digestion; but there <loes appear 

 to be a rudimentary organ by which this fluiel is driven throtugli 



