OF THE RHIZOPODA IN GENERAL:— LOBOSvV. 23 



seen to extend themselves from the surface of each vesicle (fig. 10) radiating fibres, resembling 

 those of the simple TlialassicoUa niichata. The central part of the mass is hollowed out by 

 numcrois vacuoles of considerable size, closely pressed together ; and these sometimes coalesce 

 into a single cavity, so that the aggregate body (which sometimes attains the diameter of an 

 inch) is in the condition of a hollow sphere. In another form of the same group, distinguished 

 by Midler as Collosphcpra Huxlaji, the aggregate body (which seems to correspond in all 

 essential particulars with the preceding) is included within a clear, transparent, brittle, siliceous 

 envelope, fenestrated by numerous rounded apertures (fig. 14). In this type (which seems to 

 approximate to the Fohjcystina) there are no spicules, but each spheroidal vesicle contains a 

 few prismatic crystals. 



Order LOBOSA. 



21. Amcebin A.*— Returning now to our starting-point — the most generalized type of 

 Rhizopods — we find in the Amwha and its allies (some of which are inhabitants of almost 

 every pond that is tenanted by aquatic plants, whilst others ai'e marine) a condition wliich, as 

 in some respects transitional towards the Infusoria, has caused Prof. Miiller to distinguish them 

 as " Infusorial Rhizopods." The body of the Amaha, which may vary in diameter from 

 l-2800th to I-70th of an inch, cannot be said to possess any definite shape, its outline being 

 determined by the form and number of its pseudopodian prolongations, which are processes 

 of the body itself, into which the endosarc often passes as well as the ectosarc, and not merely 

 extensions of the latter, as in Actinopkrijs. Both in form and number these arc continually 

 undergoing change ; sometimes they are all retracted, so that the shape of the body is simply 

 spheroidal (PI. I, figs. 16, 17, a); sometimes it puts forth a few broad, short, lobated expansions 

 (fig. IG, B, c) ; sometimes these are more numerous, slender, and elongated, assuming a radial 

 direction (fig. 15, A, B, c, d) ; and occasionally they are so greatly multiplied, radiate with 

 such regularity, and taper so uniformly from base to apex, as strongly to resemble the pseudo- 

 podia of Adiiiophri/s (fig. 18). The varieties thus presented have been designated under 

 different specific names ; but, as MM. Claparede and Lachmann have justly observed, the 

 grounds of such distinction will appear far from sufficient, when the vemiix\ii&)\e poIi/morpJdsm 

 characteristic of this type has been duly allowed for. 



22. The distinction between the endosarc and the ectosarc is far more clearly 

 marked in Amoeba than in Adinophrys -, the former being much more fluid, whilst the consistence 

 of the latter is much firmer. It is through the endosarc alone that those coloured and 

 granular particles are diffused, on which the hue and opacity of the body depend ; the 

 ectosarc, which forms a layer of greater or less thickness around it, being perfectly pellucid. 

 The surface layer of the ectosarc in some forms oi Amoeba (as A. bilimbosa) seems almost to 

 attain a membranous consistence, a distinct double contour being visible all round the body 

 when at rest (fig. 17, a). Still, it cannot be said that even in such cases the body is 



* On this family, see especially ii, xi, xxii, xxiii, xxv, .xxvir, xxxiii, xxxvi, xxxviii, 



LXXXII, LXXXIV, XCIII, XCVII. 



