152 Proceedings of the Royal Irish Academy. 
21st. The occurrence of ''eozoonal features" solely in crystalline 
or metamorphosed rocks, belonging to the Laurentian, the Lower 
Silurian, and the Liassic systems — never in ordinary unaltered deposits 
of these and the intermediate systems — must be assumed as completely 
demonstrating their purely mineral origin. 
Considering how rapturously its advent into palaeontology was 
greeted bj?- latter-day biologists, and others who were content to accept 
on mere authority a plausible yet one-sided explanation of a difficult 
problem, considerably beyond the ordinary means of proof, or disproof — 
considering, as is conclusively shown by the course of the discussions 
which have taken place since we first made our views public, that it can 
only be maintained by parrying, ignoring, misrepresenting, or futile 
attempts at refuting every counter argument and evidence urged from 
mineralogical, and other points of view"^* — the constructors of the 
" creature of the dawn" have certainly no grounds for exultation at its 
present position as a received doctrine" in exact science. 
POSTSCHIPT. 
The reading of the foregoing paper was followed by a short communi- 
cation from Dr. Dawson, on two points," | which it is now necessary 
to notice : — 
One relates to some fragments of Silurian crinoids, the cells and 
tubes" of which are in the state of casts composed of ''amorphous 
hydrous silicate of alumina and ferrous oxide, with some magnesia and 
alkalies," also, "angular and partially rounded grains of quartzose 
sand" — evidently a super-aluminous example of the widely varying mix- 
tures, known as glauconite, green earth, &c. The case is interesting : 
but, never having denied the well-established fact that foraminiferal 
shells, corals, and other organisms occur with, siliceous in-fiUings of the 
kind — and having already determined the attempt to assimilate such 
substances with a certain class of minerals to be utterly unsupported by 
any proper evidences — we do not see the pertinency of introducing it 
(and some others made known last year by Dr. Carpenter, J) into the 
rocks of any geological period" {Nature, No 62) ; forgetting that, as the sub- 
stance of such fossils has undergone so much change, the fact demands a vast 
amount of metamorphism to convert the rocks containing them — "least altered" as 
they may be— into the "highly crystalline condition" of " eozoonal" ophite. 
But Dr. Carpenter seems to misunderstand the objection altogether ; as it is not 
based so much on the mineral structure of the " eozoonal features," as on the fact 
that they occur best preserved in " highly crystalline " or metamorphosed rocks. 
* We beg to refer the reader to two letters in Nature (No. 62 and 72) by Dr. Car- 
penter, especially the last one, in reply to the well-founded objections to " Eozoon" 
that have lately been put forward by Mr. T. Mellard Reade, as showing the argu- 
ments and tactics now adopted in defence of the organic doctrine. 
t Proceedings, R I. A., New Series, vol. i., pp. 129-131. 
X Quart. Jour. Geol. Soc, vol. xxvi., p. 415. 
