Natural History of the Infusoria. 331 



1. Polytoma is an animal. 



2. It is characterized by a clear investing membrane, which 

 does not consist of cellulose ; two contractile spaces in the sub- 

 stance of the body ; a nucleus with a nucleolus ; two filaments ; 

 and by the deposition of layers of starch -like granules. 



3. The starch-granules may become converted into a blue or 

 green colouring matter. 



4. Polytoma divides within the investing membrane into two, 

 four, or eight parts, and propagates itself in this manner. 



5. It passes into a state of repose. 



II. Difflugia Enchelys, Ehrenberg. 



A Rhizopod occurred in company with Polytoma in all infusions, 

 the description of which will show, how very readily it might be 

 supposed to be produced by a metamorphosis of the latter ani- 

 mal. Unfortunately I cannot confirm this supposition, and 

 must confine myself to recording the fact. From its extraor- 

 dinary transparency the examination of this creature was not 

 without interest. 



The Rhizopod in question has a transparent, membranous 

 case, of an oval form, somewhat spherical on one side. The 

 substance of the body is either attached uniformly to the interior 

 of this case, or lies detached from it in various forms (figs. 16, 17, 

 18, 19). The substance of the body projects from the narrower 

 end of the case, forming that moveable portion, which may be 

 shortly characterized as the foot. In the hinder end there is a 

 round, reddish nucleus, with a white nucleolus, which is only 

 distinguished from that of Polytoma by the greater breadth of 

 the reddish halo. The foot can exhibit the most various forms. 

 In its simplest state it is nothing but a transparent globule, which 

 afterwards divides into two or more smaller ones. From these 

 smaller processes are given off, and sometimes an indefinite num- 

 ber of tentacles with acute or rounded extremities is formed. 

 These tentacles are frequently drawn out to such an extent as 

 only to present the appearance of thin rays. Sometimes also the 

 foot is branched, and then usually encloses granules of foreign 

 matter in its ramifications. The reception of nourishment is 

 probably effected by means of the foot, in exactly the same man- 

 ner as in Amoeba* The granules of food occur at first only in 

 the anterior portion of the substance of the body, which then 

 usually has a folded appearance, while the hinder portion re- 

 mains full and round. By degrees the whole body becomes 

 filled, and the nucleus almost concealed. Vacuoles are. seen in 

 all parts. The contractile spaces are probably only concealed 

 from sight, but I was unable to discover them. 



