ABSTRACT
In reply to Mr. Kitton’s animadversions on my two papers recently published in the ‘Microscopical Journal,’ I venture to make a few remarks. To resent the temper of his criticisms could subserve no useful purpose, and therefore I refer to it merely to express my sincere regret that the intrinsic value of the remarks should have been depreciated by the tone in which they have been expressed. It is not unnecessary to say that I have been for very many years devoted to the study of the Diatomaceæ of Ireland, and have carefully examined many thousands of gatherings made by me, in all parts of the country and at all seasons, and have never attempted to publish any forms as new until the Arran dredgings of Dr. E. Percival Wright were placed by him in my hands. I do not make this statement of facts for the purpose of arrogating to myself a right to speak on the subject with an authority equal to that which Mr. Kitton has assumed, but of vindicating myself from the charge of being a novice in the matter, and of being affected with the disease usually known as the cacoethes scribendi, which his observations not very graciously suggest.
How inapplicable are some of Mr. Kitton’s observations on dredgings to the forms found by me in the dredgings from Arran, the following letter from Dr. E. P. Wright sufficiently proves :
“MY DEAR O’MEARA,—The collection of Diatoms from Arran was made by me during the autumn of 1866, under the following circumstances. In the harbour of the larger island, and near the little island called Straw Island, I found large meadows of several species of brown Algae, such as Desmarestea ligulata, Cordaria flagelliformis, &c. On one or two days in which the wind was too strong to admit of dredging in the open bay, I made a large collection of these different Algæ. The dredge was thrown into water of some seven or eight fathoms’ depth at low water, and dredged along into water of such a depth that the boat would just float. I brought the material thus gathered to the hotel for the purpose of searching it over for minute Crustacea, Annelids, &c., &c. ; and being struck on several’occasions, when examining it with a low power (1 objective) of the microscope for Foraminifera, with the number of Diatoms present, I dried the weed in the sun, and then shook off all or the greater part of the fine particles adherent to it. This siliceous dust I gave to you. I also brought a small basketful of the weed with me to Dublin, and having steeped it for some hours in about two quarts of distilled water, I filtered it gradually through a muslin strainer, and gave you a bottleful of finely divided mud that passed through. One very small stream of fresh water flowed into this bay, a fact that may account for the presence of fresh-water forms in the Arran gathering. I feel very certain that all the Diatoms were attached to the Algæ, and were not taken on the ground, as, owing to the quantity of sea-weed, the dredge did not scrape the bottom.—Ever very sincerely yours, ET>W. PERCIVAL WRIGHT, Leet, on Zoology Dub. University.”
It will, doubtless, seem strange to most readers that Mr. Kitton should have ventured to pronounce his judgment on the forms referred to without having had an opportunity of examining them. Had he vouchsafed to ask, I would have gladly supplied him with some of the material, and then he would have been in a better position to form a judgment, and more weight would attach to his opinion.
I cannot forbear to express the surprise I experienced on the perusal of his paper to find that one so sharp to detect what he regards as the mistakes of others, and so forward to expose them, should himself have been guilty of such inaccuracies as the following—inaccuracies I cannot attribute to any other cause than a hasty and superficial perusal of the papers he undertook to criticise.
“Navicula pellucida, O’M., fig. 2, is a state of Navicula Pandura of De Brébisson.” In my paper, N. pellucida is fig. 3, and to it his observations are utterly inapplicable. I suppose he intended to refer to N. denticulada, fig. 2, which does exhibit some general resemblance to N. Pandura, though at the same time the difference is so marked and so constant, as not only to justify but as I think to require a distinct name.
Again, “Raphoneis liburnica, O’M., fig. 8.” In my paper this form is referred to in the following terms :—Raphoneis liburnica, var., fig. 8. By the word, he has omitted, and the letters he has unwarrantably introduced, Mr. Kitton charges me with claiming this designation as my own, whereas I attributed it to Grunow, and represented the form described by me merely as a variety of Raphoneis liburnica of that distinguished author.
Again, at page 16, we read, “Cocconeis divergens, fig. S, may be the same,” &c. Although no form so named occurs in my papers, that to which I suppose he intended to refer is Cocconeis clavigera, which is so dissimilar in all respects to C. costata of W. Gregory, as well as to Raphoneis Archeri, it is difficult to comprehend how they could be confounded.
These inaccuracies, however, although evidences of carelessness, do not materially affect the judgment pronounced, but the same cannot be said regarding the following mistake.
Page 14, “In the following observations I have assumed the amplification in the first paper to be the same as in the second, viz., 600 diameters.” Now, the amplification in the second paper is not invariably 600 diameters, as the words referred to would lead the reader to suppose. In some instances, as indicated in the table, it is 800 diameters ; and in the description of the figures, which accompanied the first paper, the amplification is plainly stated to be 400 diameters, and not 600, as was assumed.
As regards the forms in my papers which have happily escaped animadversion, it is to be presumed they are exempt from objection; and if so, enough remains to attach considerable interest and value to the Arran gatherings.
But as regards the forms which have provoked the censure of Mr. Kitton, what is his judgment, and by what process has he reached it ?
“The following forms described in Rev. E. O’Meara’s papers may, I think, be referred to previously described species.” It is difficult to understand how his remarks on Pinnularia divaricate are reconcileable with tins form of expression. They are to this effect. “Pinnularia divaricata, O’M., fig. 7, if correctly figured and described, can neither be a Pinnularia nor Navicula, as none of these genera have forked striæ or costæ.” On the assumption, then, that the figure and description are correct, and I can assure him that they are, this form, in Mr. Kitton’s opinion, must be separated from these genera—must, in fact, be assigned to a nezv genus. How incongruous the opinion thus expressed with the previous statement, so far as the form in question is concerned, “the following forms may, I think, be referred to previously described species.”
The decision Mr. Kitton has pronounced is expressed with so much doubtfulness, and so much that is conjectural, as might reasonably, in my opinion, have suggested the propriety of dealing with the subject in a gentler tone. But to give colour to the verdict as it stands it is necessary to supply the deficiency of facts from the suggestions of imagination. It is necessary to presume that the forms are imperfectly figured and described—that I am not capable of discriminating between a central nodule and a small grain of quartz that chance has thrown in the position—that the sculpture in certain portions of the valve has been obliterated by abrasion—that a certain peculiarity of structure is nothing more than an abnormal marginal development. How far such presumptions are warrantable, and what weight is due to a judgment reached by such a process, I leave’to others to decide.
Some of Mr. Kitton’s remarks I freely acknowledge, on mature consideration of them, appear not without some reason to support them, though many others, as I think, afford ample justification to doubt their accuracy.
Having carefully re-examined my specimens of Navicula Wrightii, I have no hesitation in expressing my conviction that the absence of sculpture in the spaces on either side of the median line is perfectly normal, not a trace of striæ is to be found throughout their entire length, while on the marginal portion of the valve the striæ are in all cases perfectly distinct, and exhibit no traces of the valve having been subjected to the process of abrasion. The general resemblance, indeed, between Navicular davala, N. Hennedyi, and N. Wrightii is so obvious that I consider future systematisers would be warranted in so modifying the descriptions of these forms as to include them under one denomination, but so long as the two former are regarded by the authorities as distinct from each other the last has a right to be regarded as distinct from both.
It is not improbable that Raphoneis Jonesii and Raphoneis Moorii might be advantageously classed with Cocconeis scutellum, to which they bear in some respects a strong family resemblance, but a careful inspection of the valve, and, as I think, a careful consideration of the figures and descriptions, would convince that Mr. Kitton’s opinion that they belong to one and the same species is untenable. The sculpture in the two forms exhibits a much greater diversity of structure than is considered sufficient in other forms to mark diversity of species. The figures, unhappily, were printed off without being submitted to me for correction, but to obviate the mistake which mere inspection of the figures might lead to, I added to my original descriptions of the forms such further particulars as I considered necessary to convey a clear conception of the difference between them so obvious to the observer. If these forms be referred to Cocconeis scutellum, they differ from any I have seen in nature, or in the figures of such authors as have come under my notice, and seem entitled to be regarded as undescribed and distinct varieties.
On this subject I may remark further that Mr. Kitton appears to confound what I call the border in Raphoneis Jonesii with the cingulum or hoop which unites the two valves of the frustule ; the latter is separable, as he observes, but the former, as an essential portion of the valve, is not altogether an insignificant character of the structure.
Before Mr. Kitton’s remarks came under my notice, the valuable German publication sup>1 Hedwigia ‘had made me aware that the specific name of gracilis had beeir previously applied to a form of Surriella, and I had determined on the first occasion that offered to correct my mistake, and give the name Gracillima instead of Gracilis. Grunow’s figure was familiar to me, and I know not how the name escaped my notice when examining his list, as well as others, to ascertain whether the name I had selected had been anticipated. Mr. Kitton’s remarks on Surirella are at variance with the views of the highest published authorities on the subject; Dr. Gregory and Dr. Greville, as he frankly acknowledges, differ from him. Pritchard and Grunow in their classification of the genus Surirella make use of those differences in the outline of the valve and the structure of the costæ, which Mr. Kitton considers of little value. Surirella lata and S. fastuosa are regarded by these authors, as well as by Smyth, as distinct species. Both the species I have described occur frequently in the Arran dredgings ; the forms belonging to them respectively differ little in outline, and invariably exhibit the peculiarities in the shape and arrangement of the costæ which I have noticed in my descriptions. Supported by the example of these authors, so illustrious in this department of science, I considered myself—and still consider myself—justifiable in giving distinct names to these forms of Surirella.
In addition to the characters already referred to, I avail myself of the present opportunity to notice a peculiarity in the general structure of these forms, which strengthens my reasons for separating’ them from S. fastuosa. On the side view the valves in these species are flat, whereas in S. fastuosa the centre is deeply depressed, and in the front view, although the valves are larger than those of S. fastuosa, their breadth is considerably less.
When Mr. Kitton suggested that Pinnularia constricta may be “possibly a form of Navicula truncala, a very variable species both in size and costee,” I presume he referred to a species so named in Dr. Donkin’s interesting paper published in thefMic. Journal,’ Jan., 1861. The side view of Dr. Donkin’s form is not described, and from a careful comparison of my form with his figure I considered they were distinct. In any case the specific name of Truncata for that form must be dropped, because Kiitzing, in his ‘Bacillarien oder Diatomeen,’ taf. iii, fig. 34, and taf. v, fig. 4, has figured and described a form with this specific name which bears no resemblance to Pinnularia constricta.
But further, some of Mr. Kitton’s conjectures seem to me untenable, except on principles which would have the effect of involving the classification of the Diatoms in utter confusion ; for if Navicula denticulate is to be confounded with N. pandura—N. amphoroides with Amphora salina (in which case I must assure Mr. Kitton that the suggestion so ungraciously offered in the “query,4 is not the nodule a small grain of quartz ?” is the baseless figment of his fancy)—Raphoneis Archeri with Cocconeis costata or C. clavigera—Eupo- discus excentricus with Coscinodiscus minor—the hope of dis-tinguishing species with any reasonable certainty must be abandoned in despair.
In the case of Raphoneis Archeri there is nothing to sustain Mr. Kitton’s conjecture that the puncta have been abraded. Since the paper describing it was published, the same form has been found by me in considerable abundance on seaweeds from the Falkland Islands and from Kerguelen’s Land. In the structure of Eupodiscus excentricus there is not even a remote resemblance to that of Coscinodiscus minor. Had Mr. Kitton identified it with Coscinodiscus excentricus, he would have had some reason to support his view, for in this form the sculpture is similar to that of Coscinodiscus excentricus, a fact which suggested the name. This form frequently occurred in the dredgings, and invariably exhibited the peculiarities noticed—a smooth submarginal border, and distinct processes on the secondary surface. Even suppose it be conceded that the former is, as Mr. Kitton suggests, “an abnormal marginal development,” he has not accounted for the latter, namely, the processes which seem to remove the form from the genus Coscinodiscus, as defined by the latest published authorities on the subject.
In common with many who have devoted their attention to the study of the Diatoms, I entertain the opinion that the system of classification requires and is capable of much improvement. Generic characters might be more satisfactorily defined than they are at present, and more comprehensive specific descriptions might be adopted -, and by this means the existing nomenclature might be advantageously reduced. I hope and expect that the promised work of Herr Th. Eulenstein, whose extensive experience and sober judgment eminently qualify him for the task, shall soon supply the desideratum, and place the classification of the Diatoms on a basis more simple and more satisfactory than the present.
But Mr. Kitton, as it appears to me, would apply the knife before the patient is prepared for the operation. Deep-seated and long-standing maladies may be allayed, perhaps, by superficial applications, but will certainly return unless the remedy be of such a nature as to reach the seat of the disease. That our department of science has been embarrassed by an excessive nomenclature must be obvious to every experienced observer. The evil is traceable in some considerable degree to the fact that the descriptions of species are not as comprehensive as they might be. When, therefore, the student, in the course of his investigations, discovers forms similar to some he finds described, but at the same time exhibiting constantly some peculiarities not noticed in the description, he has no alternative but that of either adopting a defective description or of marking the peculiarities he has noticed by some distinctive name. By the adoption of the former course he relieves his memory at the cost of exactness ; by choosing the latter he secures precision, though it be at the expense of a tax upon his memory. This latter method I regard as the more scientific, and that which will eventually prove more efficacious to remedy the evil and obviate its recurrence for the future.
Impressed with this conviction, and with this object in view, I consider the proper course for the student is to adopt the existing descriptions of species, to note carefully all constantly occurring deviations, and to mark them by a distinctive name. By such means his labours will increase the materials for the construction of a more satisfactory system of classification ; and if this result be ultimately attained, they whose observations have been conducted on this principle will be amply consoled for the animadversions their method may have occasionally provoked.
