438 PEOP. ALLMAN ON THE EECENT RESEARCHES 



stantly changing their shape from fusiform to spherical. They 

 take in coloured food through the cilia-disk, though no constant 

 mouth could be detected. 



From the stage represented by the isolsitedcilisi-cell, Maffosphtsra 

 next passes into the condition of a genuine Amoeba (H). In this 

 stage it appears as a simple naked nucleated cell, like all genuine 

 Amcebce. The pseudopodia are thin, conical, and pointed, like 

 those of Auerbach's Amoeba actinopJiora or his A. bilimbosa. The 

 nucleus and contractile vesicle are still present, as in the isolated 

 cilia- cell, and we can distinguish, as in most of the true Amoebae, 

 an external firmer layer and an internal softer one. Solid food 

 is taken in as in the isolated cilia-cell. The ingestion, however, 

 is not, as in the latter, confined to a definite spot, but may take 

 place indiflferently from any part of the surface. 



The Amoeba-^tSige would seem to close the cycle of development ; 

 and though Haeckel has not succeeded in actually following up 

 its life-history, it seems pretty certain that after the Amoeba has 

 increased in size by the reception of nutriment, it once more 

 encysts itself and returns to the egg-stage with which our exami- 

 nation began. 



In this most remarkable life-history, MagospTicera has passed 

 successively through the following stages : — 



1. A unicellular resting stage, indistinguishable morphologi- 

 cally from a genuine egg (A). 



By a process of cleavage which in all respects resembles a true 

 vitellary segmentation this passes into 



2. The condition of a multicellular ciliated sphere, in which it 

 resembles a form of the Volvocineoe (E). 



3. A simple isolated cilia-cell, representing the condition of a 

 peritrichal ciliate Infusorium (F). 



4. An amoeboid cell indistinguishable from a genuineAmoeiba (H). 

 The characters thus presented by iLTayospA^era appear to Haeckel 



to justify him in regarding it as a member of his group of the 

 Protista ; and from the fact of its representing in the cycle of its 

 development so many different independent forms, he makes it 

 the type of a distinct section of this group, to which he assigns 

 the name of Cat all act a. 



MagospJicera, however, would seem to be related to the Infusoria 

 at least as nearly as to the Ehizopoda. It is plainly a transition- 

 form by which the one group passes into the other. 



