it has induced Mr. Springer to prepare and publish his excellent paper, which has removed many difficulties and placed the whole subject in a clearer light and on a firmer basis.

Here I should have liked to stop; but there are in my friend's paper many remarks that show me in an unenviable aspect, and make it appear that my scepticism was not justified and that my criticism was not kept "within its legitimate bounds." I deeply lament this feeling, and have already expressed to Mr. Springer my regret that it should have been aroused by any words of mine. In writing the paragraphs to which he objects, I was most anxious to combine courtesy and friendliness with a clear exposition of my doubts. It appears that I did not succeed, and an apology is therefore due to the surviving representative of Messrs. Wachsmuth & Springer.

C

This said, I would like to explain what my criticism was and why I still think that it was legitimate. I have never denied the existence of pores in any genera in which they are now proved to exist. Nor have I ever been prejudiced for or against their presence in one genus or another. O the contrary I have always looked for them and attempte to draw them in those specimens that circumstances ha led me to study. The results of my investigation have bec to show that certain definite appearances supposed to pores were not really so, aud that pores did not exist in co tain genera where their existence was either asserted or co jectured, or at least implied by the more general stateme of eminent authorities. Mr. Springer (not to menti Lovén, Wachsmuth, and others) admits the accuracy of: observations, and therefore can not, without fresh eviden venture to ascribe pores to Cyathocrinus, Thenarocrinus, Bo ocrinus, Euspirocrinus, Streptocrimus, Mastigocrinus, Gissocri "and possibly the Cyathocrinidæ generally." This is a c siderable admission, and perhaps I should have been tent to let the matter rest there. But when I came to amine the grounds on which Messrs. Wachsmuth & Spri continued to assert the existence of pores in other gen nothing led me to suppose that they had before them st tures of a totally different character to those which I ha

and others had turned out to be nothing but depressions. lying between the folds, and that such appearances in a similar position were exceedingly common, and were correlated in many cases with the existence of articular surfaces on the edges of the raised folds as described and figured by me in Mastigocrinus and Botryocrinus. Pores and articular structures could not well coincide, but ligament-scars might easily be taken for pores. Mr. Springer chooses to regard my "few hundreds" as a rhetorical exaggeration; he will therefore be interested to learn that of Inadunate crinoids. showing the ventral sac, there are over four dozen from a single horizon and locality in the British Museum alone, that the numbers in the Swedish State Museum are certainly larger, and are rivalled by those in the Woodwardian Museum at Cambridge, while I have also examined more specimens than I can remember in dozens of other museums. This being so I really cannot have my statements disputed in toto," although I will no longer attempt to extend it to genera of which I have not made a special study. In fact I am now able to confirm Mr. Springer's statement as regards the position of certain appearances in some American species from my own observation.

But, why, it may be asked, was I formerly so ready to extend my conclusions to the specimens studied by Wachsmuth and Springer? The answer to this is my second reason. The first time that those acute and careful investigators alluded to these structures they wrote as follows: "The plates of the ventral sac in the Cyathocrinidæ are usually compartively large, rather thin, hexagonal pieces. The pores perforate the plate at each angle."* In "Cyathocrinida" they then included all Inadunata, and since they never, to my knowledge, withdrew this statement as to the pores being at the angles, I had no reason to suppose that "in the Poteriocrinida . . . without exception the position. of the pores is the exact reverse of that stated by"- Wachsmuth & Springer. Further, they have never lost an opportunity of stating that the supposed pores are on the suture lines and "never penetrate the inner portions of the plates like the water pores of the Neocrinoidea." (See "Revision" III, p. 66, p. 83, and "Perisomic plates," p. 361). I cannot

find that they have ever modified this statement either, and indeed Mr. Springer appears to intend confirming it in It is no doubt correct so far as present

his present paper.

knowledge goes.

Since, then, these statements fully agreed with my own. observations I was not a little surprised to find adduced as "most complete evidence" of pores passing through the plates, figures that not merely made no attempt to delineate the passage of the pores, but that showed the alleged pores in positions where their presence had never been asserted or had actually been denied. All this without one word of elucidation. What was one to suppose? The simplest explanation seemed to be that that the passage of the pores was, after all, too obscure a phenomenon to be shown; that the pores themselves were very difficult to see; and that the artist instructed to draw them had, therefore, in some instances inserted them in the wrong positions. Such an event is not uncommon, and if one points it out one is not generally considered to be accusing an author of misrepresentation, still less of wilful intent to deceive, I however, with no direct evidence at my command, merely "suggested" it as a possible explanation. Mr. Springer is so fairminded in debate and so zealous for the truth that he has felt it right to make admissions which show that my suggestions were not so far out after all. We need not reckon up the pores and see whether the balance of correctness is in my favour or his. Is it not enough justification for my suggestion that out of eight figures (2a, 2b, 4, 5, 7, 8, 9, 10a) showing pores, no less than five have an appreciable quantity incorrectly placed. Mr. Springer admits this for 2a, b, and 5; he does not seem to have noticed apparent pores at the angles of the plates in the distal region of fig. 4; as for 7 and 8, they may be absolutely correct drawings, but I should be sorry to have to infer the position of the pores from their evidence; the apparent pores in the cup and proximal portion of the sac of fig. 6 are unexplained; fig. 10a (Coeliocrinus ventricosus) is passed by without comment on page 134 of the paper before me, although the very clear appearances of pores must all be incorrect or deceptive according to the canon laid down on page 138 by Mr. Springer. There

*Revision of the Palæocrinoidea" 1, p. 9 of author's copy; 1879.

remains only fig. 9 (Aulocrinus) to give undoubted evidence as to the position of the pores. But how was anyone, in the absence of that special mention which Mr. Springer still finds so unnecessary, to judge between fig. 9 and fig. 10? To charge the authors with having told their artist to falsify any of the figures on their plate vii would not be a "serious" or "deadly" accusation; it would be mere childishness, for no one would intentionally publish figures that were mutually contradictory. But after reviewing the whole case in the light of the frank, lucid and exhaustive account now given to us by Mr. Springer, I can only repeat my opinion that some explanation of the differences from other figures and observations should have been given, and that in several respects scepticism has been more than justified.

SOME CURIOUS MATTERS ILLUSTRATIVE OF

GEOLOGICAL PHENOMENA.

By B. K. EMERSON, Amherst, Mass.

Plates XXI and XXII.

I The dependence of crystallization on character of surface.

Figure 1.

Many years ago when president Edward Hitchcock was professor of all the sciences in Amherst College, he had a laboratory in the cellar of the old chapel which was familiarly called Hades.

When the room was dismantled I found on a shelf a small bottle which had manifestly contained ammonium sulphide. The fluid had evaporated by capillary escape through the space between the neck of the bottle and the glass stopper and an incrustation of sulphur distinctly crystalline and thick enough to be yellow encircled the bottle about in the middle, showing the hight to which the fluid rose when it was last placed on the shelf. The upper half of the bottle between this ring and the bottom of the stopper was marked by two systems of concentric rings closely resembling the lemniscates of color in the polarization figure of a biaxial crystal. This was depicted on the inside of the glass by films of sulphur so thin as