137 
Acanthocystis spinifera (Greeff). 
In my preceding fasciculus I gave a description of a new 
form appertaining to the genus Acanthocystis (Carter), named 
by me Acanthocystis Pertyana,' and on discussing its relations 
and resemblances, under the head of ‘Affinities and Differ- 
ences,” I had naturally occasion to contrast that form with 
the one it most approaches, the above-named Acanthocystis 
spinifera (Greeff),” and I drew attention to the distinctions 
between the two forms, which, indeed, still appear to me to 
hold good. 
That occasion afforded me also the requisite opportunity to 
give a résumé of Greeff’s views and ideas as to the supposed 
or conjectured further developmental stages, or at least 
assumed modified conditions of his form. He conceived, 
namely, that the yellow globules occurring in the body- 
mass of A. spinifera, becoming extruded therefrom, involved 
in a hyaline covering, then give off opposite pencils or tufts 
of very slender and delicate pseudopodia, and at last ac- 
quire characteristics of which he gives figures.* Further, 
he conceived that these afterwards may become combined 
into considerably larger groups, the slender and delicate 
pseudopodia being now confined to the outer or circumferen- 
tial parts of the cluster or aggregation of such bodies, of 
which he also gives a figure. The first of these forms, as I 
then adverted to, is identical with that previously named 
Diplophrys Archeri (Barker),> and the second with Cysto- 
phrys oculea (mihi),® and I followed up a review of that por- 
tion of Greeff’s memoir by some considerations which 
appeared to me to render his views thereupon, as yet at 
least, improbable, and therefore to indicate that those names 
should stand. 
Amongst those considerations opposed to Greeff’s conjec- 
ture touching A. spinifera and the other forms alluded to, 
was adduced the negative, and far the least important one 
indeed—that is, that whilst the latter occur with us not very 
uncommonly, the former had not yet been found in this 
country. 
1 «Quarterly Journal of Microscopical Science,’ Vol. X, N. 8., pp. 101-3. 
2 Greef: ‘Ueber Radiolarien und Radiolarien-artige Rhizopoden des 
siissen Wassers,” in Schultze’s ‘Archiv fiir mikrosk. Anat.,’ Bd. v, p. 493, 
t. xxvii, figs. 20-3. 
3 Loe. cit., figs. 26-28. 
4 Tbid., fig. 29. 
® «Quarterly Journal of Microscopical Science,’ Vol. VIII, p. 123. 
§ Ibid, Vol. IX, N.S., p. 265. 
