llECENT MEMOlilS ON I'RESIIVVATER Rfll^OfODA. 2^7 



gaining a footing in the development-cycle of these simple 

 organisms ; it would seem as if this process may have at first 

 originated in an adaptation to external circumstances — such 

 as the drying up of the circumambient medium or after copious 

 nourishment, in order to digest at leisure, fortified against 

 surrounding foes — and that it became only afterwards turned 

 to use as a reproductive process. 



As to the limitation and afiinities of the group here under 

 consideration, the authors point out that amongst Protozoa 

 the Gregarina and Ciliata stand the most remote, for the 

 formation of trichocysts, muscle-strige and a cuticle pre- 

 sent the first beginnings of a true tissue-formation in uni- 

 cellular organisms ; in them locgmotion and alterations of 

 the figure of the body are performed by definite organs. In 

 the Ciliata there exists a definite " mouth " (Cytostoma), 

 and both have a reproductive process not directly to be 

 subordinated to simple cell-division. 



In the Acineta, special organs for the absorption of nutri- 

 tion are present, pointing to a higher grade of development. 



Amongst " Protista," the Noctiluca, Flagellata and Catal- 

 lacta are separated by the development of fiagella and cilia 

 as a more highly differentiated group. 



The Mycetozoa and Radiolaria, in the mode of the inception 

 of nutriment and of locomotion, Avould a^^proximate to this 

 group ; but the former, by reason of the peculiar complica- 

 tion of the process of development, assume an exceptional 

 position; Avhilst the Radiolaria, on the other hand, by the 

 possession of a " central capsule," as well as of true " cells " 

 embedded in the body-sarcode, are raised to a degree of 

 develojunent and differentiation, elevating them considerably 

 above the Polythalamia and Heliozoa, with which Hackel 

 has combined them in the class of the Rhizopoda. 



Thus for the present group — of the Protista, only the Poly- 

 thalamia and Heliozoa — of the Protozoa, only the Amoebina 

 and Monera would be left. These about correspond to the 

 extent of the group Rhizopoda, as founded by Claparede and 

 Max Schultze, and as generally received. The name 

 " Rhizopoda " might therefore be retained for the group as 

 a whole, but the authors suggest a new name therefor 

 owing to the following reasons. 



The name " Rhizopoda " takes its origin from the supposed 

 resemblance of the pseudopodia to the roots of a tree. 

 Such a comparison manifestly is inapplicable to the broad- 

 lobed processes of a Difflugia or Arcella, and altogether loses 

 its force applied to the flow and current of the body of an Am- 

 oeba, or the uniform rotating motion of a Hyalodiscus. They 



