OF THE RHIZOPODA IN GENERAL :—LOBOSA. 25 



by their elongated radiating pseudopodia, tliey are continually moving over the field of the 

 microscope, and receiving into their bodies any small substances which they may happen to 

 encounter in their progress. This movement is effected by the protrusion of some part of 

 the periphery of the body into a pseudopodian process of greater or less elongation : towards 

 this process, and usually for some way into it, there is a current of the internal granular 

 substance; at the same time there is a retraction of any processes of the like nature which 

 might have been previously put forth from the other side of the body, and a reflux of the 

 granular substance from these towards the centre ; and by a continuance of this change) 

 the entire Ijody is gradually advanced in the direction of the new extension. The kind 

 of motion thus executed by an Amaeha is described by most observers as a " rolling" action, 

 this being certainly the aspect whicii it commonly seems to present ; but it is maintained by 

 MM. Claparede and Lachmann, as the result of a very careful observation of certain forms 

 of Amceba that present peculiarities in the disposition of their parts which render them (so to 

 speak) "test objects" as to this point (such as the A. quadrilineata of Carter, and the A. Umax 

 of Auerbach), that the appearance of rolling is an optical illusion, for that the nucleus and 

 contractile vesicle always maintain the same position relatively to the rest of the body, and that 

 " creeping" or rejjfafion would be a more true description of their mode of movement. On 

 this view, these animals have their ventral surface constantly differentiated from their dorsal, 

 it being from the former alone that the pseudopodian extensions proceed ; and thus a tran- 

 sition would seem to be indicated towards the testaceous Ammhinm, in which the dorsal 

 surface is invested by a shell, and the pseudopodia are strictly limited to the ventral. 



26. When the body of an AiiifEha, or one of its extensions, comes into contact with any 

 small particle, the movement of the former very commonly presses it against the latter with 

 sufficient force to cause it to make its way through the ectosarc into the cavity of the 

 endosarc ;* and thus tlie latter may often be seen to contain Diatomacca, Desmidiacece , frag- 

 ments of larger Algm, Infusoria, Boti/era, and even Entomostraca, with an occasional 

 intermixture of inorganic particles. These undergo a kind of circulation in the general 

 cavity of the interior, which is maintained, as just shown, by the movements of the sur- 

 rounding contractile substance; and tliis circulation (like the movement of the contents of 

 the stomach in higher animals) doubtless promotes the digestive process. The larger masses 

 that are available for nutriment are gradually broken up into finer particles ; and these seem 

 to constitute the granules which are always to be seen diffused in greater or less abundance 

 through the liquid interior of the endosarc, the colour of those granules being pretty 

 obviously the same as that of the matters ingested, and the effects of chemical reagents upon 

 them being identical. Insoluble bodies appear to be rejected from time to time, by making 

 their way towards the surface, and then penetrating the ectosarc at the point which happens 

 to be nearest, just as they are in Adinophrys. 



* Whilst admitting that there is uo evidence of the existence of a constant definite oral aperture 

 iu Ammha, MM. Claparede and Lachmann tliink it conceivable that there may be such an aperture, 

 of which the lips might be exactly applied to one another, as in Amphileptus, so as only to open at the 

 moment of deglutition. They express themselves as certain, that in their Podostoma filigerum (^ 28) 

 such a definite oral aperture exists (xxv, p. 418). 



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