258 Description of the Plates. 



nucleus and nucleolus, by the Amoebina and Actinophryna, 

 differentiates them from the other Rhizopoda, and has 

 caused them to be placed in a separate order, as ' Infusoria 

 Ehizopoda,' or ' Rhizopoda Sphyg-mica.' The Actinophryna 

 differ from the Amoebina in having- their granular cen- 

 tral parenchyma carried by circulation into the interior of 

 their pseudopodia, which also are delicate and filamentous, 

 and anastomose apically, like those of the Foraminifera and 

 Radiolaria; but they resemble the shelless Rhizopod here 

 figured, not only by possessing* the structures b and c, but 

 also by enveloping* alimentary substances within their paren- 

 chyma, as the Amoeba is seen to do at d and e. At the 

 same time, the circulation which takes place in the pseudo- 

 podia of the Actinophryna is to be borne in mind as favour- 

 ing endosmosis, and thuSj though it is much less ener- 

 getically carried on in them than in the typical Rhizopoda, 

 enabling them to extract nutriment from their prey by the 

 same suctorial process which is the single method by which 

 those animals absorb nutriment. 



d. Navicula, one of the Diatomaceae, swallowed as food. 



e. Spore of conferva enveloped as nutriment by the parenchyma 



of the body. It is only in the larger specimens that these 

 vegetable remains are found ; and it is rare in any Amoeba 

 to find any traces of any other kind of nutriment. The 

 action of digestion is shown by the decolorization of the 

 chlorophyll, as well as by other changes effected in the 

 ingesta. It does not seem possible to demonstrate the pre- 

 sence of an external enveloping membrane in the Amoebina, 

 except in Amoeba billmhosa, unless reagents be employed, 

 which themselves probabl}^ cause the differentiation observ- 

 able after their use. And there does not seem to be any 

 positive reason for supposing that these animals possess a 

 mouth which is only opened at the moment of swallowing, 

 and has its lips so closely appressed at other times as to 

 make the aperture invisible, as is the case in the Infusorial 

 genus Amphileptus. The absence of mouth, anus, differen- 

 tiated tegumentary envelope, and cilia, must be held to 

 justify the separation of Amoebina from the Infusoria, with 

 which however they are placed by Kolliker and V. Carus, 



