LOBOSA 743 



much more closely in its characters to an ordinary ' cell ' composed 

 of cell-wall and cell-contents. It is through the ' endosarc ' alone, 

 E 1ST, that those coloured and granular particles are diffused, on 

 which the hue and opacity of the body depend ; its central portion 

 seems 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.' 

 The ectosarc, E C, which is perfectly pellucid, forms an almost 

 membranous 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 ; l and thus there is no evidence, in Amoeba and its immediate 

 allies, of the existence of anymore definite orifice, either oral or anal, 

 than exists in other rhizopods. The more advanced differentia- 

 tion of the ectosarc from the endusarc of AiiH?l><i is made evident 

 by the effects of reagents. If an Amceba radiosa be treated with 

 a dilute alkaline solution, the granular and molecular eiidosarc 

 shrinks together and retreats towards the centre, leaving the radia- 

 ting 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 envelope noticed by Colin as possessed by Para- 

 mecium and other ciliated Infusoria, and with the containing mem- 

 brane of ordinary animal cells. A ' nucleus,' N", 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 presents the aspect of a clear flattened vesicle 

 surrounding a solid and usually spherical nucleolus ; it> is readily 

 soluble in alkalies, and first expands and then dissolves when treated 

 with acetic or sulphuric acid of moderate strength ; but when 

 treated with dilute acid it is rendered darker and more distinct, in 

 consequence of the precipitation of a finely granular substance in 

 the clear vesicular space that surrounds the nucleolus. A ' contrac- 

 tile vesicle,' C V, seems also to be uniformly present, though it 

 does not usually make itself so conspicuous by its external prominence 

 as it does in Actinophrys ; and the neighbouring part of the body 

 is often prolonged into a set of villous processes, V I L, the presence 

 of which has been thought by some to mark a specific distinction, 

 but which seems too variable and transitory to be so regarded. 



The pseudopodia, which are not appendages, but lobate exten- 

 sions of the body itself, are few in number, short, broad, and rounded ; 

 and their outlines present a sharpness which indicates that the 

 substance of which their exterior is composed possesses considerable 

 tenacity. No movement of granules can be seen to take place along 

 the surface of the pseudopodia ; and when two of these organs come 



1 This remarkable character has been staled by Professor Huxley in the following 

 admirable sentence : ' Physically the ectosarc might be compared to the wall of a 

 soap-bubble, which, though fluid, has a certain viscosity, which not only enables its 

 particles to hold together and form a continuous sheet, but permits a rod to be passed 

 into or through the bubble without bursting it, the walls closing together, and re- 

 covering their continuity as soon as the rod is drawn away.' 



