252 
Acanthocystis Pertyana, sp. nov. (PI. XVI, fig. 1.) 
Acting on tlie 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). 1 
But whilst this is the base, 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 
Actinophrys brevicirrhis hut the data given by that observer 
being scanty, and the figure not sufficiently explanatory, this 
must remain somewhat 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 Claparede and 
Lachmann quote a form, which they refer to Actinophrys 
brevicirrhis (Perty), as common about Berlin; 3 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 abun- 
dant. 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 of these being long and averaging in length 
more than the diameter of the body, the other set short and 
hardly averaging a third of the length of the longer ones. 
The periphery of the body seems to be covered by a stratum 
of short, somewhat curved spicula, held together in some not 
readily perceived manner into what Carter called a ‘ lorica,’ 
and enclosing the sarcode body. The pseudopodia stand 
forth in all directions, of necessity issuing from amongst the 
1 * Annals of Natural History,’ 3rd Ser., vol. xiii, p. 36. 
3 ‘ Zur Kenntniss kleinst.er Lebensforinen,’ p. 159, t. viii, fig. 7. 
3 ‘ £t,udes sur les lnfusoires et les Rhizopodes,’ p. 450. 
