3 ’ 
April 3, 1873) 
_ tributions have been made to this branch of scientific 
_ Study by Prof. Palmieri, who so courageously stuck to his 
observatory on Mount Vesuvius throughout the whole of 
the tremendous eruption of 1872. The symmetrical form 
of the craters of many volcanoes is very remarkable, in 
some instances the outline of the cone and crater being 
absolutely perfect in its symmetry, as in the case of the 
volcano of Rangitoto, of which a plan and section here 
reproduced is given in the work. 
Our space forbids our entering more fully at present into 
the merits of these interesting volumes. G. L. B.G, 
LETTERS TO THE EDITOR 
[The Editor does not hold himself responsible for opinions expressed 
by his correspondents, No notice is taken of anonymous 
communications. ] 
Dana on Corals 
A Reply To THE Criticism or Mr. DuncAN 
IN a criticism of Prof. Dana’s work on Corals and Coral 
Islands, printed in a recent number of NATURE (vol. yii. p. 119), 
Mr. Duncan has seen fit to mention my name and certain of my 
views adopted by Dana in a somewhat discourteous manner. I 
therefore beg leave to reply, as briefly as possible, to some of his 
strictures, which are both erroneous and unjust. 
Concerning the general character and plan of Dana’s book it 
is not my intention to say anything, for those are matters which 
chiefly concern the author and publisher. It is to be presumed 
that they know, quite as well as any critic, the kind of book 
demanced by the public—at least by the American public—and 
experience every day shows the errors of critics in this respect. 
Certainly few authors have had more extensive and successful ex- 
perience in writing strictly scientific books for the public than 
Prof. Dana. 
Mr. Duncan criticises the introduction of brief notices and 
descriptions of ‘‘animals which are not corals, and which in no 
way affect or produce coral reefs or islands,” evidently alluding 
to the Actiniz, Hydroids, and. Bryozoa; for he says, “ all the 
notices and descriptions of the Actinize and Hydroidea might have 
been omitted, as they only confuse the subject.” Surely Mr. 
Duncan ought to know, and if he does, should not ignore the 
fact, that Millepora, and the allied genera, are true Hydroids, 
and at the same time form large and abundant corals, which con- 
tribute very largely to the formation of coral reefs and islands 
both in the Atlantic and Pacific Oceans. Moreover, this im- 
portant fact is stated by Dana on page 104 of his book, and its 
discovery is correctly attributed to Avassiz, while the animals are 
illustrated by a cut copied from his figures. It should be added 
that this discovery, made twenty five years ago, has recently been 
confirmed by Pourtales (‘‘ Deep Sea Corals,” p. 56, 1871). 
That many of the ancient fossil corals were of the same nature 
scarcely admits of doubt, although the writer has elsewhere 
shown that this was not the case with all the so-called ‘‘ Tubu- 
lata.” Why, then, should this important class of corals be 
omitted from such a work? As for the Actinice, their relation- 
ship to the ordinary stony corals is so close, both in external ap- 
pearance and internal anatomy, that no general work on corals 
could be considered at all complete without an account of them. 
Their physiology is also much better known than that of the coral 
animals, Moreover, they are the only near relatives of the true 
corals that the majority of the readers of the book will ever see 
alive. . 
The Bryozoa are also quite entitled to the page and a half 
allowed them in this book, for that they do contribute something 
to the existing coral-reefs can be easily demonstrated. One species 
of escharella, abundant on the eastern coast of the United States, 
forms solid coral-like masses often two or three inches in dia- 
meter, which accumulate in large quantities over w de areas, and, 
under fayourable circumstances, would form limestones of con- 
siderable thickness, Some of the coral-reef species grow still 
larger and occur in profusion. In the Palgeozoic coral-seas and 
reefs the Bryozoa were of still greater importance, and s me of 
the so-called “ true corals” of tho-e times evidently belonged to 
this group in addition to those usually referred to ic. ‘The stony 
Algz also, are by no means to be ignored in treating of coral 
reefs, and the half page devoted to them might well have been 
extended rather than omitted. Darwin, Agassiz, Major Hunt, 
NATURE 
423 
and others besides Dana, have recognised their agency in furnish- 
ing calcareous matter to the reef limestones, Fine specimens of 
such limesiones, composed aimost entirely of their remains, may 
be seen in many Am-rican museums. 
Mr. Duncan, in criticising Dana for adopting the classification 
which he believes most natural, makes this remark : ‘* The intro- 
duction of American novelties to the exclusion of well-recognised 
European classifications, is neither right nor scientifically cor- 
rect.” Are we to infer from this that “ American noveltics ” are 
less valuable than French or English ones, providing they be equally 
true to nature? Or does our critic prefer European error to Ame- 
rican truth? Certainly no one has contributed more, in the way 
of original investigations and discoveries, to a true classification of 
the corals than Dana himself, in his great work on the Zodphytes 
of the U.S. Exploring Expedition, which was far in advance of 
any work on this subject that had been written in Europe up to 
that time (1846). In some respects his classification was far 
more natural than that proposed afterwards by Edwards and 
Haime, Unfortunately at that period most of the corals and 
polyps in European museums had not been described or figured 
by European writers in a manner accurate enough to make their 
identification possible, or even, in many cases, to show their 
generic and family characters. That Edwards and Haime, 
having access to those collections, and having the benefit of 
Dana’s great work, should have been able to make corrections 
and improvements was natural. Nor was it less natural that, 
after the publication of the more accurate descriptions and 
figures in their works, an American, having these and all the 
other works.at hand, with constant access to the original types 
of Dana, to the unrivalled collections of corals brought together 
by Agassiz,and to all the other collections in the United States 
(by no means few or smali) should, after devoting a large part of 
his time for twelve years to the special study of corals, have 
been able to make still other corrections and improvements, 
even in opposition to the views of certain European writers, 
But several European authors have also made numerous changes 
in the system of Edwards and Haime, and are likely to make 
many more, Certainly the time has not yet come when we can 
consider the classification of corals permanently fixed. 
Whether the “novelties” to which he refers be ‘* scientifically 
correct” is quite another question, and one that must be settled 
in the scientific way, by the evidence of facts observed, and not 
by denunciations, nor by dogmatic assertions. In selecting 
examples of the supposed inaccuracies of my views, as adopted 
by Dana, Mr. Duncan cites the ‘‘Oculina tribe,” which the 
writer has established to include not only the Oculinide, but 
several other families, referred by Edwards and Haime to the 
Astrzeidz and elsewhere. He says—‘‘ The admission of Orbi- 
cella, which is really tne old Astrae of Lamarck (not of 1801), 
and of Caryophyllia into this well-differentiated tribe, is simply 
absurd, for they possess structural characters sufficiently diverse 
as to place them in different families.” As a matter of fact, the 
writer has placed these same corals in different famelies in several 
papers published during the past five years, and this is the view 
adopted by Dana; so the argument quoted becomes ‘simply 
absurd.’’ Again, he says that ‘* Astrangia was well differentiated 
long before Prof. Verrill was heard of,” and adds that Conrad 
Lonsdale and ‘the distinguished French Zodphytologists 
consolidated the genus, which has nothing in common with the 
Oculinidz.”” What he means by ‘‘ consolidated” in this connec- 
tion, it is difficult to tell, for all that Conrad and Lonsdale did 
was to describe very poorly, under the name of “ Astrze,” two 
or three fossil species, which Edwards and Haime afterwards 
referred coubtfully to Astrangia. The genus itself was first 
pointed out by Dana in 1846, and named Pleiadia, as stated in 
his book, page 68 ; but it was not at that time strictly defined, 
for there were no spccies in the collections of the Exploring Ex- 
pedition ; consequently tne name Astrangia, proposed two years 
later, has been universally adopted. Dana's oriyinal specimens, 
with the MS. names placed upon them in 1845, stil exist in 
our collections. But what my own age or reputation in the year 
1848 has to do with the matter 1s not obvious. I trust thateven 
then I was old enough to have seen the absurdities of such a 
criti.ism as that under discussion. That I hive, since that time, 
carefully studied sixteen species of that geuus and described a 
large number of new ones, while only three were known to 
Edwards and Haime, is true. That ] have shown the close re- 
lationship between this genus and Clad cora and Oculinais equally 
ue, and I presume that had Mr, Duncan enjoyed as goou op- 
portunities as I have had for studying this and all the related 
