In the previous number of this Journal, the Rev. E. O’Meara has charged me with carelessness, and thinks if I had read his papers with greater attention I should have expressed my doubts of the genuineness of his new species more cautiously. I have, therefore, read them again, in order to apologise for any misrepresentation, and correct any errors. I find two or three mistakes; viz., Cocconeis divergens should have been C. clavigera, the remarks on Navicula pellucida ought to have preceded the passage quoted by the Rev. E. O’Meara. I have also inadvertently made him the author of Raphoneis liburnica, whereas he is only responsible for the variety. With these exceptions, I really find nothing to retract. At page 91, the Rev. E. O’Meara says : “How inapplicable are some of Mr. Kitton’s observations on dredging to the forms found by me in the dredgings from Arran.” I find, on referring to his first paper, he says, “this material was procured from depths varying from ten to thirty fathoms,” &c. I do not think, therefore, I was unjustified in assuming that his material was similar to others procured from like depths, and which, in almost every case, consist of sand, animal and vegetable debris, and valves of diatoms. My copy of the ‘Microscopical Journal ‘in which his first paper appears has no description of the figures. I therefore assumed that the figures were magnified 600 diameters, as that was the degree of amplification more frequently used in the second paper. I do not find the number of diameters stated in the text. If the Rev. E. O’Meara refers to the text of his first paper, he will find Navicula pellucida is fig. 2 ; and fig. 2 in the plate is the form which, I think, resembles Navicula pandura much too elosely to entitle it to rank as a new species*. N. denticutala is fig. 3 in text. I am still unconvinced of the specific distinctness of Surirella pulchra and S. gracilis, or that they differ sufficiently from?. lata to warrant their separation from that species. I am willing to admit that a remarkable difference exists between the figures of S. pulchra and S. gracilis; viz., the crenulate margin ; alæ are also wanting, but as these differences are not noticed in the text, I am inclined to doubt the correctness of the figures, and suppose the crenulations represent the undulations of the alæ, and that the margin of the valve is not shown in the figure.

Mr. Roper, at page 17, vol. viii, of this Journal (Campylodiscus productus). says: “The markings and canaliculi on most species of Surirella are subject to considerable variation, and afford no good grounds for specific distinction.” Professor W. L. Smith, who has long studied the habits of living diatoms (quoted by Dr. Lewis in his valuable paper on “Extreme and Exceptional Variations of Diatoms”), says: “When I find Navicula amphirynchus congregating, and producing Navicula ferma, Stauroneis gracilis producing S. Phænicenteron, and Surirella splendida S. nobilis, quite different in form and striation, I cannot but doubt the propriety of making new species out of every different FORM AND MARKING.”

Eupodiscus excentricus I still refer to Coscinodiscus minor* of Kutzing (not of the synopsis), and, after a careful examination of many specimens from various localities, I find the excentric areolation precisely as figured by the Rev. E. O’Meara, and in he majority of cases a circle of obtuse spines may be easily seen. I do not, however, find any with what I suppose to be an abnormal marginal development, as shown in E. excentricus.

The Rev. E. O’Meara says, that a careful consideration of the figures and descriptions of Raphoneis Jonesii and R. Moorii would convince that Mr. Kitton’s opinion, that they are identical, is untenable. “The sculpture in the two forms exhibits a greater diversity in structure than is considered sufficient in other forms to mark diversity of species.” I have carefully compared the figures, and to me the sculpturing seems to be precisely the same in both forms ; take away the margin, and it would be impossible to distinguish one from the other. I saw that the description did not accord perfectly with the figure, but as it was nowhere stated that the figure was erroneous, I had no means of knowing which was correct. The suggestion that Raphoneis Archerii might be the upper valve of Cocconeis clavigera is not so difficult to comprehend when the structure of the genus Cocconeis is understood ; the difference between Raphoneis Archerii and Cocconeis clavigera is not greater than that between the upper and lower valves of Cocconeis Grevilli.

Stauroneis rhombica, n. sp., O’M., appears to resemble Stauroneis apiculata of D. Greville (in ‘Edinburgh New Philosophical Journal/July, 1859) much too closely to warrant its separation from that species.

The Rev. E. O’Meara remarks, “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 that the descriptions of species are not as comprehensive as might be.” Surely the reason why they are not so, obviously arises from the circumstance of so many new genera and species being constituted from unique or rare specimens, and until the system of making new species of scarce forms is abolished, this evil will continue. Before a species can be correctly described, it is necessary to see it in a living condition, and, if possible, its sporangial form. A botanist, before he published a new species, would require to see more than a few leaves. In conclusion, I venture to quote two or three authorities whose opinions are of infinitely greater weight than mine.

Dr. Berkeley (in the preface to his ‘Cryptogamic Botany’) says: “So long as essential characters are neglected, and fleeting external characters put in their place, difficulty must needs exist, and the student will never be certain that he has come to a correct decision till he has seen an authentic specimen, or compared his own with that of other botanists, as manifested in extensive herbariums. A state of uncertainty is always one of more or less pain, and the temptation to a solution of the difficulty by the supposition that he has made a new discovery present such attractions as to appear insurmountable. Nor will he find it possible, without that mental discipline which arises from a patient study of every detail of structure, and of the various shapes which organs may assume under different circumstances. The great point in all cases is never to describe from single or imperfect specimens, where there is-some form evidently very closely allied. A proposer of bad, ill-defined species is no promoter of science.” Another acute observer (Dr. G. A. W. Arnott), whose knowledge of diatoms is perhaps superior to that of any other observer of those forms, says, in his paper on “Rhabdonema ”(vol. vi, p. 87, of this Journal), “That it is better not to publish a new species, or give it a name, than to do so from scanty or imperfect material, which leaves both genus and species doubtful. Even now I have some hesitation in writing on the subject, as my views are diametrically opposed to those who consider it necessary to give names to forms which to the eye appear distinct, but which have not structural differences sufficient for a specific character; and this alone entitles them to he acknowledged and referred to by others.” And again, at page 106, “Microscopical differences are by themselves of little importance. To see is one thing, to understand and combine what we see is another. The eye must be subservient to the mind. Every supposed new species requires to be separated from its allies, and then subjected to a series of careful observations and critical comparisons.

“To indicate many apparently new species is the work of an hour ; to establish only one on a sure foundation is sometimes the labour of months or years. A naturalist cannot be too cautious. It is better to allow diatoms, to remain in the depths of the sea, or in their native pools, than, from imperfect materials, to elevate them to the rank of distinct species, and encumber our catalogue with a load of new names, so ill defined, if defined at all, that others are unable to recognise them. The same object may be more easily obtained by attaching them in the mean time to some already recorded species, with the specific character of which they sufficiently accord. In all such cases, the question to be solved for the advantage of naturalists is not whether the object noticed be a new species, but whether it has been proved to be such, and clearly characterised.”*

Dr. Carpenter, in the preface to his introduction to the ‘Study of Foraminifera,’ says : “But nearly a parallel case, as regards the first of these points (the derivation of a multitude of distinguishable forms from a few primitive types) as presented by certain of the humbler groups of the vegetable kingdom, in which it becomes more and more apparent from the careful study of their life history—not only that their range of variation is extremely wide, but that a large number of reputed genera and species have been created on no better foundation than that afforded by transitory phases of types hitherto only known in their state of more advanced development.” “And the main principle, which must be taken as the basis of the systematic arrangement of the groups of Foraminifera and Protophyta, that of ascertaining the range of variation by an extensive comparison of individual forms, is one which finds application in every department of Natural History, and is now recognised and acted upon by all the most eminent botanists, zoologists, and palæontologists.”If my previous paper was wanting in courtesy, as the Rev. E. O’Meara seems to think, I can only say that it was unintentional, and beg to apologise for it; my only desire was to protest against the addition of so many “new species,” their claim to that position (in my opinion) being more than doubtful. I could, if I thought it desirable, publish a score or two of new species, if the fact of their appearing different to any hitherto published is all that is necessary to constitute a new species.

*

N. denliculata of the text, is frequent in the so-called“Corsican moss”

*

This may possibly be the small form of C. excentricus figured ‘Synopsis’.

*

Since the above quotation was written, I have to deplore the loss of my old friend and correspondent, — a loss that will be acutely felt by all who have had the pleasure of corresponding with him. He was at all times most willing to assist the student with information and specimens.