EHIZOPODA LOBOSA : AMCEBA. 



443 



to have an almost watery consistence, the granular particles being 

 seen to move quite freely upon one another with every change in 

 the shape of the body ; but its superficial portion is more viscid, 

 and graduates insensibly into the firmer substance of the Ectosarc. 



Fig. 234. 



Amceba princeps, in different forms, a, b, c. 



The Ectosarc, which is perfectly pellucid, forms an almost mem- 

 branous investment to the endosarc ; still it is not possessed of 

 such tenacity as to oppose a solution of its continuity at any point, 

 for the introduction of alimentary particles, or for the extrusion of 

 effete matter ; and thus there is no evidence, in Amoeba and its 

 immediate allies, of the existence of any more definite orifice, 

 either oral or anal, than exists in other Rhizopods. The more 

 advanced differentiation of the Ectosarc and the Endosarc of 

 Amceba is made evident by the effects of re-agents. If, as Auerbach 

 has shown, an Amoeba radiosa be treated with a dilute alkaline 

 solution, the granular and molecular Endosarc shrinks together and 

 retreats towards the centre, leaving the radiating extensions of the 

 Ectosarc in the condition of csecal tubes, of which the walls are not 

 soluble, at the ordinary temperature, either in acetic or mineral 

 acids or in dilute alkaline solutions; thus agreeing with the enve- 

 lope noticed by Cohn as possessed by Paramecium and other ciliated 

 Infusoria, and with the containing membrane of ordinary animal 

 cells. A Nucleus is always distinctly visible in Amceba, adherent 

 to the inner portion of the Ectosarc, and projecting from this into 

 the cavity occupied by the Endosarc ; when most perfectly seen it 



