ON THE RADIOLARIA AS AN ORDER OF THE PROTOZOA. 371 
the difference between fact and mere guesswork, and are there- 
fore singularly out of place. 
But despite all drawbacks, in attempting to advance the Com- 
posite Thalassicollidce into the front rank of the ££ Radiolaria,” 
Mr. Mivart has rendered us a signal service by so directing 
attention to them that it has become absolutely indispensable 
that the Radiolarian classification should be revised, and the 
proper location for the Thalassicollidce determined. Whilst this 
is being effected it would be well to ascertain whether the 
Noctilucce might not with propriety be referred to the same 
group. It is true that nothing is as yet known of the reproduc- 
tive process of these remarkable and common organisms. But, 
after all, knowing too little is better than knowing too much. 
Time and patience usually suffice for the discovery of missing 
links ; but neither time nor patience is profitably expended in 
proving negatives. 
As for the ££ streaming of granules ” and the occurrence of 
^seucfo-pseudopodia imbedded within the extra-capsular sarcode 
of some of the Thalassicollidce , both phenomena are present also 
in Noctiluca. And, to say the least of it, inasmuch as not a 
single example is producible of endogenously projected and 
active pseudopodia occurring within the body substance of any 
true Rhizopod, we have in this distinction a character which 
furnishes the very antithesis of an ££ approximative ” bond 
between the former organisms and the latter. 
Mr. Mivart alludes to the discovery by Haeckel, since his 
“ Die Radiolarien ” appeared, of the remarkable ££ Myxo- 
trachia ,” which Haeckel associates with his “ Polycyttaria ,” or 
compound Radiolaria . Not having seen this creature, I can 
form no definite ideas as to its relations. But I do not hesitate 
to affirm that, if the figure given of it is accurately drawn, 
although it may be a Radiolarian in Sir Wyville Thomson’s 
sense, it is unquestionably not a Rhizopod, and that nothing 
could more forcibly demonstrate the purely arbitrary character 
of this classification than the admission of so palpably distinct 
a form, even allowing the fullest scope to Mr. Mivart’s reserva- 
tion that it is ££ a curious and exceptional form.” 
Before passing on to the concluding section of this article, I 
may be permitted to say that it is highly gratifying to find 
from Mr. Mivart’s memoir that ££ Hertwig has strongly insisted 
(as I did fifteen years ago) upon the greater importance of A 
Nuclear Vesicle as a classificatory character than any characters 
which can be derived from the skeleton”; (Memoir, p. 173), 
and that Mr. Mivart ££ quite agrees that it forms a most import- 
ant distinction, which he therefore proposes to adopt provi- 
sionally, fully bearing in mind that it may hereafter be very 
widely, if not all but universally, present in the group,” adding 
B B 2 
