and other Indigenous Rhizopods. 447 



body, the perfectly regular or irregular outline of the latter, and 

 even trifling modifications in its colour, have been accepted as 

 specifically valid*. 



Why, then, it may be asked, have I referred the Hampstead 

 form to A. Eichhornii ? I reply, solely because the characters 

 presented by this variety are those which appear to me to illus- 

 trate in the same individual the true offices and relations of the 

 several parts of the Actinophryan structure to each other and 

 to allied genera, and ought therefore to be regarded as typical 

 of that genus. 



The Hampstead form, like the Amoeba already described, is 

 unusually large, at times attaining a diameter of joth of an 

 inch, irrespectively of the pseudopodia. Whilst I write, I have 

 a number of living specimens before me, obtained two months 

 ago, in which the entire structure is so pellucid and definite 

 that it can be resolved with a common pocket-lens. The shape 

 is spherical, not discoidal, under ordinary conditions, even when 

 the creature is adherent to the sides of the glass vessel in which 

 it is contained, — this being reconcileable with a fact I can 

 attest, namely, that the surface of the body does not come in 

 contact with the glass, but is entirely supported by the tenacity 

 of the intervening pseudopodia. The sarcode substance is 

 colourless, as is the sarcode of all Amcebans and Actinophryans, 

 except under abnormal .circumstances. The pseudopodia are 

 sometimes long, sometimes short ; at times perfectly rigid and 

 smooth, at times slightly tuberculated and sinuous. When 

 rigidly extended, they never coalesce; when bent and supple, 

 and more especially when about to encircle some food-particle in 

 their inevitable embrace, they coalesce as freely as those of the 

 Foraminifera. Now and then, but rarely, the vacuolation, so 

 universal and marked in the form as it most constantly occurs 

 at Hampstead (fig. 1), is partially superseded by the coalescence 

 of a number of the cell-like cavities, and the ectosarc or endosarc 

 exhibits the aspect of ordinary unvacuolated protoplasm, and we 

 may more legitimately apply the terms " medullary " and " cor- 

 tical" to the inner and outer portions of the organism. But 

 physiologically there exists no such permanent distinction of 

 parts. There is invariably a line of demarcation between the 

 " cortical " and " medullary " portions ; but the most careful 

 analysis of the structure, even when assisted by the highest 

 powers of the microscope, does not enable us to detect the 



* If the characters of A. oculata are correctly drawn, and if, as asserted, 

 food does not pass into the " medullary " substance, but remains during 

 the assimilative process within the " cortical " layer, that form must not 

 only be regarded as specifically distinct, but as presenting a feature which 

 is quite anomalous in the group to which it belongs. 



