ON THE RADIOLARIA AS AN ORDER OF THE PROTOZOA. 279 
able ; but, on the other hand, very many Radiolaria, according 
to Hertwig, depart widely from the spherical form ; and simi- 
larity of chemical composition * cannot, therefore, be considered 
a distinction of great weight, seeing that such similarity is 
shared with many other lowly organisms of quite different 
affinities. (Memoir, p. 181.) 
With reference to the reproduction of the Radiolaria , Mr. 
Mivart informs us that it “ undoubtedly takes place by means of 
numerous zoospores, each with a nucleus and flagellum, but 
with no vacuoles ; whereas in the Heliozoa the much fewer 
separated reproductive parts have each two flagella as in most 
rhizopods (!), several contractile vacuoles , and a nucleus , with 
vacuoles and nucleoli .” These differences he considers as so 
great that he warns us (as indeed he well may, considering that 
he does not shrink from laying down as regards the reproduction 
of the Radiolaria “ by spores ,” that “ it is certain that such a 
process occurs in Acanthometra, Thalassicolla , Sphcerozoum , 
Gollosphcera and Gollozoum, and most probably in all the 
Radiolaria.” (Memoir, p. 167.) And again, that “ 6 there are 
also great differences in this respect between different Heliozoa , 
while the reproductive processes of so few Radiolarians have 
as yet been examined , that it would be rash to feel confident 
that no important divergences will hereafter be found to exist 
among them in this respect! ” (Memoir, pp. 180, 181.) 
I candidly confess to feeling confounded, and at an utter loss 
even up to this point to reconcile these seemingly diametrically 
opposed opinions ; or to comprehend what 66 further important 
divergences ” should be needed than the all important one to 
which Mr. Mivart himself draws attention, and constitutes No. 
4 in his list of distinctions categorically given (at p. 180) be- 
tween the Radiolaria axi&Heliozoa ; namely that “yellow cells 
are present in almost all Rhizopods, but absent in Heliozoa ; ” 
that is to say if he, or rather those writers on whose opinions he 
is placing his trust, choose to insist that because the sarcoblasts 
of the freshwater Actinophryans , in common with the rest of 
* I have been altogether unsuccessful in tracing to whose chemical 
analysis of these microscopically minute structures we are indebted for this 
apparently decided judgment upon their elementary constitution. Under all 
the circumstances I would humbly suggest that it will be a iong time, indeed, 
before any differences in the chemical composition of such subtle organisms 
can be determined by any re-agents at the chemist’s command. In the very 
nature of things, identity, or apparent identity, must be far more easily indi- 
cated. But be this as it may, when it is borne in mind that it is unreservedly 
asserted that “ The Radiolarians live on Algae, Diatoms, and Infusoria, and 
other small animal and vegetable organisms found near the surface of the 
sea,” it must, indeed, be a difficult task to ascertain where chemical analysis 
is dealing with the mere animal’s body, or with its victuals. 
