an elevation mentioned by Loomis occurred in the warmer parts of this country. If his theory finds favor, and the writer's conjecture is correct, it will be presumed that the three samples cited in the Handworterbuch from the still warmer regions of the earth were taken in the midst of such a mass of cold air descending from, and retaining the composition of, the upper parts of the earth's atmosphere.

The analyses here printed should not be used in determining the average composition of the air by combining analyses from all sources. Whether the writer's conjecture is correct or not, it has enabled him to select times for taking samples of air varying widely from the average; and to such times his analyses have been commonly limited, only occasionally including a sample of presumably normal air to serve as a check on the abnormal.

Western Reserve College, Hudson, Ohio, June 12, 1879.

ART. XXVIII.-Principal J. W. Dawson's criticism of my Memoir On the Structure of Eozoon Canadense compared with that of Foraminifera; by K. MÖBIUS, Professor of Zoology at Kiel.*

If it were true that "the organic character of Eozoon is at present generally admitted," as Dr. Dawson says in his criticism on my memoir, I could have spared myself the trouble of elaborating, and others that of reading, my studies. But every one who has paid attention to this question knows that this statement of Dr. Dawson is not correct. As long as two different opinions about one object in nature are maintained, and on both sides by men whose learning and honesty in the search for the truth cannot be questioned, so long are renewed studies and descriptions of the differently judged object a scientific duty for all who believe that they have the true explanation. For every phenomenon in nature but one thoroughly true explanation is possible. This principle, as stated in my memoir (p. 178), has guided me in preparing it for the scientific public.

Dr. Dawson says further, "As fast as one opponent" (against the organic character of Eozoon) "is disposed of, another appears." And he rises, himself, to dispose of me, the last of the opponents.

* For Dr. Dawson's paper see this Journal, xvii, 196, March, 1879. [Thinking that Professor Möbius should have, if he desired, an opportunity to reply to Dr. Dawson's criticism, and that science would profit thereby, we offered him the pages of this Journal, and stated that we should be pleased if he would occupy them and give his views on the subject; informing him, at the same time (in order to remove any objections that might arise in his mind), that there would be no rejoinder in this Journal. Professor Möbius has accordingly prepared for us the article now published. J. D. D.]

AM. JOUR. SCI.-THIRD SERIES, VOL. XVIII, No. 105.-SEPT., 1879.

No one should be able to do so better than he. It was he who described the Eozoon Canadense as an organism; who has, moreover, a very fine collection of specimens of Eozoon, and has studied the Eozoon in situ and is fully acquainted with the literature relating to it. I could not, indeed, have wished for a more experienced reviewer, to show me where I had fallen into error and where I had found the truth.

It is Mr. Dawson's belief that few scientific men are in a position fully to appreciate the evidence respecting the organic character of Eozoon; that this is true of the geologists and mineralogists, because they do not yet agree with regard to the nature of the rocks in which it occurs; and of the biologists, because they are but little acquainted with the appearance of foraminiferal organisms when mineralized with silicates." "Nor are they willing," he says, "to admit the possibility that these ancient organisms may have presented a much more generalized and less definite structure than their modern successors. Worse, perhaps, than all these, is the circumstance that dealers and injudicious amateurs have intervened and have circulated specimens of Eozoon, in which the structure is too imperfectly preserved to admit of its recognition." These are the principal points in the introduction to Principal Dawson's criticism on my paper. He continues: "The memoir of Professor Möbius affords illustrations of some of these difficulties in the study of Eozoon."

I hope Principal Dawson will concede that, in my memoir, there is no evidence that the different hypotheses with regard to the geological character of the strata in which the Eozoon occurs have puzzled me; nor that any previously_conceived hypothesis has influenced me in my conclusions. To hypotheses of this kind I have briefly alluded in the last chapter of my memoir where I say: "While excluding Eozoon from the organic world by scientific arguments, it is by no means maintained that in the Laurentian period there may not have existed organisms. It is possible that the graphite of the Laurentian beds may have originated from organisms." These words ought plainly to have shown Mr. Dawson that no geological hypothesis compelled me in advance to deny the organic nature of Eozoon. On the contrary, in the beginning of my studies I hoped to gain conclusive evidence in favor of the organic character of Eozoon, as I have stated in my memoir, chapter VI: "It is to me a source of regret that I cannot say to Messrs. Dawson and Carpenter, who have so kindly aided me in my work, that Eozoon Canadense must be considered, from my researches also, a fossil Foraminifer." I quote these words here for the benefit of those readers of Principal Dawson's criticism who are not acquainted with my memoir.

I was familiar with the structure of fossilized Foraminifera, as can be seen from several notations and figures in my paper. Nor was I unwilling to admit that the structure of Eozoon might be different from that of modern Foraminifera, as is evident from the following words in my memoir (p. 188):

"If all the structures of Eozoon, in the same layers and forms that they have in the best specimens circulated by Dawson and Carpenter, were indeed produced by living beings, the living Eozoon must have had a nature totally different from that of all plants and animals we know. If it were possible to prove that Eozoon is a fossil and not a mineral, we must then make two divisions of organic bodies, viz: 1, organic bodies with protoplasmic nature (all plants and animals); 2, organic bodies with eozoonic nature (Eozoon Dawson). In the genealogical line, in which the theory of evolution or descent unites all protoplasmic beings, there is no place for Eozoon."

Further, not a single one of all the specimens of Eozoon, which I studied, came from the hands of "dealers or injudicious amateurs," but all directly or indirectly from Messrs. Dawson and Carpenter. This I have said repeatedly in my paper. I am consequently much surprised at the words of Dr. Dawson: "The memoir of Professor Möbius affords illustrations of some of these difficulties in the study of Eozoon."

Why should Principal Dawson write thus about my memoir if he has read it throughout with attention and understanding? It bears full evidence that I had not to struggle in the slightest degree with such difficulties.

But Principal Dawson has read my paper, and he points out two errors in it, viz: 1, I have (on p. 180) taken as a figure of full natural size a very large specimen of Eozoon, which Principal Dawson on plate III of his "Dawn of Life" has presented of half the natural size; 2, on the same page I say: "We know specimens of Eozoon which have more than fifty whitish and greenish laminæ," on which Mr. Dawson remarks, that they often have more than a hundred.

For these corrections I offer my sincerest thanks. Other substantial errors he has not mentioned. If he will do so, I shall be further grateful to him. For if in a paper of mine an error is unveiled, the first displeasure I feel in having not been careful enough to avoid making a mistake, is very soon effaced by the satisfaction of seeing the pure and certain truth come forth. No naturalist, in any branch of science, has ever discovered and brought out at once the whole truth in all directions. It is evident that those two mistakes are of no significance in deciding the question whether Eozoon Canadense is an organism

or not.

But Dr. Dawson writes further (p. 197): "Möbius has

had access merely to a limited number of specimens mineralized with serpentine. These he has elaborately studied, and has made careful drawings of portions of their structures, and has described these with some degree of accuracy; and his memoir has been profusely illustrated with figures on a large scale. This, and the fact of the memoir appearing where it does, convey the impression of an exhaustive study of the subject, and since the conclusion is adverse to the organic character of Eozoon, this paper may be expected, in the opinion of many not fully acquainted with the evidence, to be regarded as a final decision against its animal nature. Yet, however commendable the researches of Möbius may be, when viewed on the evidence of the material he may have at command, they furnish only another illustration of partial and imperfect investigation, quite unreliable as a verdict on the questions in hand."

On reading these lines one cannot but be astonished and ask, whether they were written by the same author, who said a few lines before: "Professor Möbius is a good microscopist, fairly acquainted with the modern Foraminifera, and a conscientious observer." This impression he must also have gained from my paper on Eozoon Canadense.

Principal Dawson, in saying I have had access "merely to a limited number of specimens" of Eozoon, should have stated exactly how many specimens are to be studied to gain a conclusive judgment in regard to its real nature. It has often happened that biologists and paleontologists have had not more than one specimen in hand, or even not more than a part of a specimen, and notwithstanding they were in a position to determine surely its place in the organic kingdom. He says, further: "Möbius has made drawings of portions of the structure of Eozoon" he does not state what structures I have omitted. I have certainly made careful drawings and descriptions of all the Eozoon-structure, which according to Messrs. Dawson and Carpenter corresponds with the chambers, the communications between them, the tubuli of the proper wall of the chambers, and the canal-system in the intermediate skeleton of Foraminifera.

Principal Dawson says again: "Möbius has described these structures with some degree of accuracy." It would have been more satisfactory if he had pointed out the imperfectious of my descriptions, each one for itself and all without reserve. I should have been grateful for the aid in improving my descriptions of Eozoon.

Principal Dawson evidently apprehends that my "profusely illustrated" paper may convey the impression of an exhaustive study of the subject. That was indeed my purpose. Has he not read or understood my remarks (pp. 178 and 179) in regard to the necessity of many good drawings of all the structures of

Eozoon? Or, had he in writing his criticism the opinion that it would be read by those only who would never see my paper itself?

66

But how can he venture to say: "The fact of the memoir appearing where it does conveys the impression of an exhausting study of the subject?" A bad paper has never gained the continued assent of the public through the fame of the Journal in which it appeared. In giving my paper to the editors of the illustrious Palæontographica" I had by no means the intention of gaining for it any higher opinion than it deserves by itself. I wished to bring it before a disinterested and judicious public; besides, I knew that the publisher of the "Palæontographica" would take care to print my drawings very exactly, and he has done so.

After having made these objections in general, Principal Dawson considers "a number of errors and omissions arising from want of study of the fossil in situ, and from want of acquaintance with its various states of preservation."

If Principal Dawson demands that nobody should venture to judge of the nature of Eozoon but those who have seen it in situ, he claims in favor of his Eozoon Canadense an exception over all productions of the accessible world. When writing these lines he overlooked the fact that Mineralogy, Paleontology, Botany and Zoology contain a very great number of universally appreciated memoirs concerning objects which the authors have never seen in situ.

It was my intention to study Eozoon from a biological point of view, which is indeed shown in the title of my memoir, viz: "The structure of Eozoon Canadense, compared with that of Foraminifera, by my own investigations."

It seems strange that Principal Dawson quotes in his criticism but the first five words of this title. If it were actually so short, many things might have been left out which the real title promises. For my purpose, the examination of Eozoon from a biological point of view, I was in a very favorable situation, because a very large number of specimens of Eozoon Canadense were at my disposal, which Messrs. Dawson and Carpenter had sent directly to me or to other naturalists.

Can I now be reproached, that I accepted all specimens of Eozoon as genuine, which the two principal defendants of its animal nature had proved! But if Principal Dawson means that my drawings and descriptions were insufficient to show all variations and all degrees of preservation of his Eozoon Canadense, I would request him urgently to send me such specimens as will enable me to improve my researches. I shall accept them with my best thanks, study them very exactly, and will bring all I shall find conscientiously before the scientific public.