132 
temporarily protrudes a greater or less number of digitate or 
tapering, short, hyaline pseudopodia, upon the retraction of 
which the extemporized openings in the investment become 
effaced by virtue of its inherent fusibility. 
Affinities and Differences—The “ nucleus” and the digi- 
tate, or short tapering pseudopodia presented by the forms 
appertaining to such a genus as the foregoing diagnosis may, 
perhaps (so far as present information goes) successfully 
define, seem at once to stamp its “ Ameban” affinity. There 
might be thought to be some resemblance—nay, close affinity, 
to Greeff’s Astrodisculus,! but the want of the so-called 
‘“* nucleus,” the presence of the ‘‘ central capsule,” and of the 
numerously exceedingly slender filiform, (not short digitate 
or conical), pseudopodia, as far as I can see, completely 
place the forms referable to that genus apart from the pre- 
sent, and amongst Radiolaria. I have no doubt that I have 
now myself met with more than one Astrodisculus form, but 
so sparingly, that I have yet had no opportunity to submit 
them to anything like a sufficient examination. But though 
the Amphizonella-forms are then “Amceban,” in their affinity 
they seem generically quite distinct from all such recorded 
previous to Greeff’s memoir, by the special and peculiar cha- 
racter of the “‘ outer coat.” Possibly, further research may 
disclose transitory stages in development of the forms refer- 
able here, which may present conditions falling short of those 
assumed as typical in the present state of knowledge about 
them, but as yet, I venture to think, the genus must be 
taken as a ‘‘ good” one. 
It seems exceedingly probable that the form named by 
Auerbach, Ameba bilimbosa,? ought to be referred here ; this 
has not, however, so far as I am aware, been ever redis- 
covered. Many of the characteristics described for it seem 
to point to a community of structure with such as-the pre- 
sent, and, therefore, in fact, to its necessary exclusion from 
- Ameeba proper, notwithstanding that Auerbach has endea- 
voured to demonstrate that ‘ all Amoebe are encompassed by 
a universally-closed membrane, which is structureless, very 
extensible, and perfectly elastic.” To combat this view, 
however, is no part of the object of this communication, nor 
to give a résumé of Auerbach’s now well-known memoir, to 
which I would refer, however, as interesting in connexion 
1 Greeff, “ Ueber Radiolarien und Radiolarien-artige Rhizopoden des 
siissen Wassers,” in Schultze’s ‘Archiv fiir Mikrosk. Anatomie,’ Bd. vy, p. 
496, T. xxvii. 
2 Auerbach, “Ueber die Einzelligkeit der Amceben,” in Siebold and 
Kolliker’s ‘ Zeitschrift fiir wissensch. Zoologie,’ Bd. vii, p. 374 (1856). 
