ARCHER—ON RHIZOPODA. OSs 
tinophrys, leaving for the latter part of this communication the consi- 
deration of another series showing affinities rather in the direction of 
the Gromida and of the Difflugiz. I shall first venture to offer some 
remarks on the forms as they thus present themselves, and defer spe- 
cial generic and specific descriptions to the end of my communication. 
Acanthocystis Pertyana, sp.nov. (Pl. [X., fig. 1.) 
Acting on the plan alluded to, the first that presents itself is a 
little Rhizopod lately detected by me, one amongst the most minute, 
but one, at the same time, seemingly very well marked. It does not, 
however, demand a new genus for its reception, as it falls, as will be 
_seen—in my opinion, at least, as a new species—under the genus 
Acanthocystis (Carter).* But whilst this is the case, there is just a 
possibility, indeed, that our form may be really identical with one of 
Perty’s, and referred by him to Actinophrys under the name of Actino- 
phrys brevicirrhis ;+ but the data given by that observer being scanty, 
and the figure not sufficiently explanatory, this must remain some- 
what a matter of doubt. But that the present form can be identical with 
Perty’s is, after all, not at all likely, though possible, inasmuch as 
Claparéde and Lachmann quote a form, which they refer to Actino- 
phrys brevicirrhis (Perty), as common about Berlin ;{ and it is hardly 
likely that the whole three observers would have fallen into the error 
of taking the present form as belonging to Actinophrys at all. 
Before, however, drawing more special attention to Perty’s form, 
or that forming the subject of this communication,_it will be advisable 
to allude to Carter’s genus Acanthocystis, thereupon to describe my 
animal, and afterwards to compare it with that of Perty. 
The type of Carter’s genus is Acanthocystis turfacea, a form not 
uncommon in our moor pools, though never abundant. At a first 
glance, and under a moderate power, it might be taken for a green 
Actinophrys, as the long spines, standing out from the circumference 
of the globose body, look like pseudopodia; but a closer examination 
reveals that these are rigid, deciduous, discoid at the base, and bifid at 
the apex; and I am disposed to agree with Carter that they seem 
tubular. They ordinarily occur of two distinct lengths, one set being 
long, and averaging in length somewhat more than the diameter of the 
body, the other set short, and hardly averaging a third of the length 
of the longer ones. The pseudopodia stand forth in all directions, of 
necessity issuing from amongst the spine-like spicula; they are very 
slender, filiform, hyaline, occasionally showing minute granules, and 
are in length rather more than twice that of the longer set of spines. 
It is, however, so far as my experience of this form goes, rare to find 
this creature with the pseudopodia extended; possibly, however, the. 
* ‘ Annals of Natural History,” 3rd Ser., vol. xiii., p. 36. 
+ Perty, ‘‘ Zur Kenntniss kleinster Lebensformen,” p. 159, t. viii., fig. 7. 
t Claparéde et Lachmann, ‘ Etudes sur les Infusoires et les Rhizopodes,’’ p. 450. 
