ARCHER—-ON RHIZOPODA. 267 
film of sarcode he supposes to be formed by the universal coalescence 
of the bases of the pseudopodia themselves.* In the forms now de- 
scribed, this layer is not formed by the coalescence of the pseudopodia ; 
for these, taking origin from the inner region, pass out directly through 
the outer, without the least appearance of any confluence. 
The other heliozoan genera forming the subject of Greef’s and my 
own communications (along with Actynophrys sol) do not present the 
character of two differentiated portions of the sarcode body. This 
appears to be similar throughout, but as the case may be, in the new 
genera enclosing or surrounded by characteristic structures. 
The following, then, may serve as diagnostic characters of the 
several forms brought forward:— 
Genus, Acanthocystis (Cartery). 
Generie Characters.—Rhizopod composed of two distinct sarcode re- 
gions—the inner dense, hyaline and with or without colouring granules, of a 
globular and somewhat rigid figure—the outer colourless, soft, and delicate 
(sometimes difficult to be discerned), bearing a number of more or less 
elongate siliceous spicula, discoid at the base, and arranged in close ap- 
proximation vertically upon the periphery of the inner sarcode body, 
which gives off, through the outer region, and reaching beyond the radiating 
spicula, a variable number of very slender, delicate, non-coalescing granu- 
liferous pseudopodia. 
It will be seen that, in the generic characters, I have claimed for 
Acanthocystis, as in some other new genera, two differentiated strata 
of the sarcode mass; the inner one is, of course, that within the cavity; 
the outer is not so perceptible, yet I think can be readily seen with 
close examination as a pale, colourless, granular, rather plastic invest- 
ment to the radial spines. It is not, I think, conceivable how these 
could originate, merely touched to the surface of the inner body mass ; 
they would not grow like a plant just in contact and no more, or even 
slightly immersed in the upper surface of the inner body: they must 
be deposited by sarcode. This outer sarcode region, I believe I readily 
see in living examples; and though I do not find it insisted on by 
Grenacher or Greef, I think I see it well depicted in the figures of the 
latter. I think that in Acanthocystis this differentiated outer sarcode 
region exists just as truly and as marked as in Raphidiophrys, Hetero- 
phrys, or Pompholyxophrys. 
It will be further seen that I have left out any allusion in the fore- 
going characters to the assumed more or less curved tangential spicula, 
described by Carter as characteristic, inasmuch as I now conceive they 
are not of any essentially different nature, nor, indeed, even necessarily, 
* Wallich “On the Polycystina,” in “ Quart. Journ. of Micr. Science,” vol. v., N. S., 
p. 71. 
¢ ‘‘Ann. Nat. Hist.,” 3 Ser., vol. xiii., p. 36. 
VOL. Y. 2N 
