68 Proceedings of the Royal Irish Academy. 
representatives. At least, I think, matters must remain as they are 
in that regard for some considerable time longer. 
The difficulties I advert to — as they appear to me — I have already 
tried as succinctly as possible to set forth, so that I need not here 
recapitulate them. I would only just mention, as connected with the 
question, that, as it would seem to me, the more the ^'Heliozoan" 
group are studied, the more closely do certain representatives of them, 
at least, appear to annex themselves to the marine " Radiolaria," but, 
yet from such, however, the transition is not abrupt to others whose 
negative characters would seem rightly enough to forbid their admission 
into that Order. JN'or is this in itself to be wondered at ; in all forms 
of organization the transitions are more or less gradual; and, as bearing 
on the relations of the Heliozoa and the Eadiolaria, it is interesting to 
note Haeckel's statement in a recent memoir (one as noble and interest- 
ing as we yet owe to his busy pen), that the young condition of a 
typical or true " Radiolarian" is morphologically that of a "Helio- 
zoan."t It is scarcely necessary, of course, to remark, still less to 
urge, that this is by no means a statement that any of the recognized 
forms which can rank only as Heliozoa are but young or progressive 
states of forms, which, in course of individual development, are fated 
to rise to the dignity of Eadiolaria. It seems, I think, as if it might 
rather be interpreted as a statement, that a young E-adiolarian indeed 
may be, from a morphological point of view, but equivalent to a 
Heliozoan ; but whilst the former, by and by, puts on additional 
characteristics, a true member of the latter group can rise no higher, 
but must remain with its fellows, to present us with a continuous 
supply, as we find them, of examples of its kind. 
Before directly passing on to endeavour to give some account of 
the forms which I have tried to pourtray in the accompanying 
drawings — one, at least, new, the others, if not new, at all events, 
seemingly comparatively rarely encountered and little-known" — I 
cannot but make use of the opportunity to reiterate my own view as 
to the seeming constancy with which the freshwater representatives, at 
least, of the Ehizopoda maintain their characteristics and special 
identities, and recur, again and again, more or less commonly or rarely. 
I cannot coincide with those who hold that their differences are but 
accidental and casual, being simply due to surrounding circumstances ; 
that, because the living part in all throughout is essentially but a little 
mass or patch of '^sarcode," and so all have a pervading uniformity 
of nature, they are, therefore, all, as it were, but one rhizopod — this 
protean creature presenting itself to view under various aspects, whose 
seeming specialities are but accidental and unessential. If, indeed, I 
have misapprehended the views of Dr. Wallich and others in thinking 
they hold the extreme opinion I have just indicated, they at least urge 
* Loc. cit., vol. X., p. 21. 
t Haeclrel, " Beitrage zur riastidentheorie ;" in " Jenaische Zeitschrift fiir Me- 
dicin und Natvirwissenschaft ;" Bd. v., page 630. 
