368 
POPULAR SCIENCE REVIEW. 
ON THE RADIOLARIA AS AN ORDER OF THE 
PROTOZOA. 
By Surgeon-Major G. C. WALLICH, M.D, &c. 
Continued from page 281. 
It is in the second order of the Rhizopods, namely, that 
which comprises the Plagiacanthidce , Acanthometrce, Thalas- 
sicolliclce ,* and Dictyochidce , that the first trace of structural 
advance is made manifest by the presence of a distinct mem- 
branous or 46 capsular ” covering to the nucleus. The more deeply 
tinted masses, of which mention was made just now in the 
Foraminifera , though not true nuclei, owe their denser appear- 
ance to the accumulation of the minute sarcodic granules, which 
are more or less uniformly diffused in the more limpid and colour- 
less portion, whilst the creatures are in their natural state. 
But there is every reason for believing that these granules are 
of the same nature, and contribute to the reproductive process 
in nearly the same way as the granules contained within the 
membranous capsule, and those present in the sarcode mass 
exteriorly to it, of the superior Order. But in this case the 
evolution of a true tissue undoubtedly indicates physiological 
advance, and hence becomes a safe Ordinal distinction. 
In those Rhizopods which are endowed with membranous 
capsules, it seems probable that nuclear granules and even sar- 
coblasts are able, by some means or other, to force a way through 
* If Hertwig’s observations on the Collosphceridce and Sphcerozoidce are as 
accurate as they appear to have been carefully made, it is evident that the 
whole of these remarkable composite forms, of course including the single 
exceptional genus Thalassicolla , ought to be removed from amongst the 
Rhizopods and placed — at all events provisionally — with the Heliozoa 
(assuming that these multiply also by zoospores, furnished with flagella, 
whether single or double), as a distinct group between the Rhizopods and 
the Gregarinidce ; inasmuch as neither the difference of habitat, nor the 
mere difference in colour of the sarcoblasts of the two families can be held 
to be a cause for their being kept distinct. 
