764 



RHIZOPODS. 



The Amoeba is remarkable for the fact that it really has no outline and no shape, 

 for its body is continually altering its figure ; so that the rounded object which was 

 seen in the microscope but a few minutes before, will, in that short space of time, have 

 protruded a number of elongations that look like fingers of a glove or the rays of a 



star-fish. 



It can elongate itself to almost any extent, can then throw out its strange protrusions 

 so as to resemble a club with a spiked head, or it can gather itself into a rude gobular 

 mass, as if pinched out of dough by a single squeeze of the hand, allowing the soft 

 substance to protrude between the fingers. It has no particular stomach, but ex- 

 temporizes that organ out of any part of its body with which its food happens to 

 come in contact, literally pushing the food into its body and then digesting it without 

 requiring any special apparatus for the purpose. 



Some of the Lobose Rhizopods, as these creatures are called, are also furnished with 

 a shelly or horny covering, such as the Arcellina, where the shield is cap-shaped or the 



Perinidium trifrta. 

 Perinidium michalis. 



Kerorta polyporum. 



Amtfba frrinceps. 

 Amoeba raditsa. 



Difflugia, where it is pitcher-shaped, the animal protruding itself from that part which 

 represents the mouth of the jug. Many physiologists suppose that the Amoeba is not a 

 perfect being, but it is merely the larval state of some animal with a higher develop- 

 ment, such as the Arcella and other shell-bearing Rhizopods. 



The genus Perinidium may be known by the furrow that runs transversely round the 

 body, and is furnished with cilia. The integument of the body is membranous. The 

 Tripos Perinidium is remarkable for its power of shining by night. It may be recognized 

 by the shelly case, which is concave, smooth, and is developed into three horns, two 

 being long and the other comparatively short. The longer horns are in front. Its 

 length is about isoth of an inch. The Kerona also belongs to this order, and is found 

 in fresh water, where it may often be seen in considerable numbers. Besides the usual 

 cilia, it is furnished with instruments of progression that enable it to climb and creep, 

 and are formed like bristles or booklets. Its length is rather variable, but is about 

 equal to that of the Perinidium. 



