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companionship of a couple more of its own species about to 
be born, would by no means satisfy its roving propensities. 
Now, the circumferential spicules of the Acanthocystis cohere 
in some way into a tough strong stratum, making a kind of 
integument, which only gives way upon force by an irregular 
rent. One meets such remains of defunct examples of 
Acanthocystis now and again. Our young rotatorian now 
repeatedly dashes headlong against this remaining barrier 
between him and freedom. Well done! little fellow! he 
has burst his prison-walls and swims away rejoicing, and 
already begins to pick up his ‘ crumbs’ in the ocean (to him) 
upon the slide. I presume we must regard the rotatorian as 
wholly a usurper here — in a great measure, a parasite. Can 
the germ of the rotatorian grow at the expense of the material 
of the body-mass of the rhizopod, which evidently vanishes 
to have its space occupied by the former ? Only when there 
are three, however, does it ordinarily all disappear. How do 
the ova originally come there ? How can the mother-rota- 
torian deposit her ova, ichneumon-like, within the ill-fated 
Acanthocystis, for the ‘ lorica’ of Carter seems intact? 
This genus differs from Actinophrys in the possession of a 
skeleton, from Clathrulina 1 in the possession of two distinct 
kinds of loose portions of the skeleton, and not a hollow 
perforate globe ; nor can such a type be referred to any of the 
marine genera of Haeckel, owing to the absence of the all- 
important character — the possession of a ‘ central capsule.’ 
In fact, Carter had no other alternative than to make a 
distinct genus for his Acanthocystis turfacea, which species 
has hitherto been the only one known, and hence the type of 
the genus. 
It may not, therefore, be without interest to draw atten- 
tion to a second form in a genus which, while it is shut out 
from the marine forms, has no very immediate relative in the 
fresh waters, at least so far as the characters to be drawn 
from the skeleton are concerned. 
The form, of which 1 now venture to refer to a rough 
sketch, tig. 1, has occurred to me in one or two places only, 
near Carrig Mountain, Wicklow, and at first glance I took it for 
apossible rotatorian ovum; for, until I made a second gathering 
from the same source, presenting a greater number of ex- 
amples, I had not the good fortune to find a specimen with 
the pseudopodia extended. But a brief inspection even of 
specimens not exhibiting the pseudopodia satisfied myself 
that it was no ovum I had before me, but a true rhizopod. 
1 Cieukowski, in ‘ Schultze’s Arcliiv fur MikroskopischeAnatoniie,’ Bd. iii, 
Heft iii, p. 311, 1867. 
