THE

MONTHLY MICROSCOPICAL JOURNAL.

OCTOBER 1, 1871.

I.-A Rare Melicertian; with Remarks on the homological position of this Form, and also on the previously-recorded new species Floscularia coronetta.* By CHARLES CUBITT, F.R.M.S.

PLATE XCVIII.

Introductory.

OCCUPIED in the prosecution of certain investigations on the homological position of the members constituting the so-called Families of Ehrenberg's Class Rotatoria, with the view to the establishment of a correct natural Classification as the basis of a work on which I am at present engaged, I find myself fortuitously placed in command of a field of operations in the instance of a small streamlet, a tributary of Northbourne Brook, in Kent, overgrown with the bladder-wort (Reticularia), which streamlet is literally swarming with every member of the following genera of Ehrenberg's system, viz. Stephanoceros, Floscularia, Melicerta, Tubicolaria, Limnias, and Ecistes, together with several of the fresh-water polyzoa; and amongst the former I find a rare Form, or at all events one which has hitherto escaped the notice of observers generally; and with the object of establishing the correct position of this elegant Form as well as that of Floscularia coronetta, it is incumbent on me. herein to review briefly the homologies of the particular Families in which they will respectively be placed.

TERMINOLOGY AND ASPECTS.

The Terminology and Aspects which have hitherto been employed, do not apply appositely to the several Forms embraced; the term lorica, for instance, signifying in its literal interpretation a coat of mail or an armour, is illogical and absurd when indiscriminately used to represent the simple hyaline investments of the solitary Floscularians, the clustered forms of the Lacinularians, or even the compound sheaths of the Melicertians. I have therefore adopted certain modifications which will be employed throughout these remarks; and for lorica we shall substitute the term Vagina. The word disk, as signifying alike the region of the tentacular crown of * M. M. Journal,' September, 1869.

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the Floscules and the ciliated lobes of the Melicertians is equally absonant, and for this we shall substitute and henceforth apply the term Corona. And following a good example in the matter of aspects, we shall employ Neural to indicate the ganglion side and Hamal the opposite, and further, shall characterize the active vibratile appendages of the corona as Cilia in contradistinction to the Setæ, which perform an intermittent action when investing the corona; and for want of a more appropriate term we must apply this also to the delicate hairs which furnish the pistons of the antennæ.

Stephanoceros Horatii.

The obvious diversity of the form and position of the corona of the Floscularians clearly and indisputably separate them from a Family association with the Melicertians in which the corona subtends the mouth; and moreover, while the members of the former manifest a true bilaterality by the preponderance of the neural margin of the corona, no such bilaterality obtains either with Stephanoceros or with the miscalled F. coronetta. The corona of the Floscularia is, as generically characterized in reference to the lobes, short, broad, knobbed, expanded; while the tentacles of both Stephanoceros and this species are long, slender, and erect; we see further that the corona of the Floscules is, with one exception, beset with setæ upon the lobes only, while the whole margin of the corona of Stephanoceros and of this species is invested in one continuous series. We see also that these two Forms are identical in other points of their economy, and are of a higher type of organization than that of the Floscules, first as regards their nervous, muscular, alimentary systems, and further in the fact that the stage which supports the tentacles of Stephanoceros and F. coronetta acts in the double capacity of the calix and lophophore of the FreshWater Polyzoa, and like these Forms they possess an epistome, which is situated just above the ganglion, they both manifest an organic attachment of the tunicle, and perform palpable invaginations of what may, for the sake of argument, be termed the endocyst with every retraction of the corona-points which establish a homological identity with the so-called F. coronetta, and Stephanoceros Eichornii, and as such it will in future be denominated Stephanoceros Horatii.

THE FAMILY MELICERTADE.

We now come to a consideration of the Melicertians, and with these we find that the corona subtends the mouth, that, whether simple or serrated, its periphery is continuous and unbroken, and is furnished with an uninterrupted range of active vibratile cilia,

* Allman's 'Fresh-water Polyzoa.'

whose procession, or the appearance of such is seen to be in one and the same direction from left to right when viewed in a neural aspect, and that it is supplemented by a secondary range of more minute cilia, whose procession is divided into two channels, emanating from the under-side of the corona in its expanded condition, and progresses, so to speak, in opposite directions, conveying the captured particles to the mouth, where they are subjected to the scrutiny of a bilobed ciliated organ, situated immediately above it, though, unlike the epistome of Stephanoceros, it is placed in a hæmal position, but it exercises a similar function in selecting the nutritive particles from the general mass, and in rejecting others, as the scrutiny may determine. This secondary range of cilia obtains, in a more or less developed condition, in every individual member of the Melicertians, whether it be Limnias, Ecistes, or Lacinularia, and it terminates in a process projecting from the ganglion side, and in most, but not all of the members, it is supplemented by a fabricating organ, which is employed in the construction of their compound tunicles, an exceptional instance occurring in a little Melicertian, which employs her voided excremental pellets to cover the otherwise hyaline investment. This fabricating organ, in its normal position, is also wanting in the instance of the elegant Form which has induced these remarks, Plate XCVIII., Fig. 1, and in bringing them to a close it will be only necessary to add that the genus Melicerta must include all those members in which the foregoing points are permanent, and that Limnias, Ecistes, and Tubicolaria are essentially Melicertians, and will be referred to as such; retaining, however, their hitherto specific appellations as for the sake of facility of recognition.

Melicerta annulatus.

My attention was first drawn to a vagina of this species, which at a glance exhibited proportions differing from any hitherto known Form, containing within it an ovum of a magnitude equally surprising. I at once applied the micrometer, and for the moment failed to notice the corrugations which, singularly enough, coincide exactly with the 2000th divisions of the micrometer; they occur as little ridges formed around the circumference of the vagina, which in all young, and young adults is perfectly hyaline, manifesting a decided and brilliant orange tint, but seen at the two sides when in proper focus they are rendered very distinct, the orange tint becomes condensed into a deep carmine. How these ridges become formed with such marvellous precision is a matter that must strike all with wonder and admiration; and although I do not feel myself prepared at once to state anything definite as to their formation, I can only suggest it as worthy of attention that the anterior regions manifest a considerable and somewhat complicated

departure from those of the other Melicertians, to which we shall give some consideration in a subsequent paragraph.

The footstalk is most frequently wrinkled, and it manifests very distinct muscular bands, see Plate XCVIII., Fig. 1; but notwithstanding the presence of these, they do not produce sufficient contraction of the stalk to enable the animal to withdraw itself within the vagina without producing folds in the footstalk, as shown by the rough sketch, Plate XCVIII., Fig. 5. The integument, which is corrugated all along the footstalk, ascends to the corona, where it forms an orifice into which the corona becomes retracted by an invagination, the line of demarcation being very distinct even during the eversion of the corona, leaving, however, the two respiratory tubes the most prominent objects in view, as is the case with every one of the Melicertians, whether these tubes are rudimentary, or otherwise highly developed.

In its retracted condition, Plate XCVIII., Fig. 2, the corona manifests two distinct projecting processes beyond the setiferous tubes which, though they present the same general appearance, are not provided with setæ, but manifest at their extremities a bright red spot under the illumination of the Wenham parabola; we do not expect to find eyes in a hæmal aspect as these spots are situated; beneath them there are three other processes which are less highly developed, and the distance between these two upper processes and the three lower ones corresponds precisely with the "pitch," or distance apart of the annulets of the vagina, and we see that although the corona is frequently protruded far above the margin of the vagina, it never remains in that position for periods of long duration, except in the instances of old animals, whose vaginæ are coated with extraneous matter, but with younger animals, the corona on the act of eversion is seen to emerge somewhat above the margin, and then to subside to such a position that these two processes become identical with its margin, suggesting the not unreasonable notion that these peculiar organs are employed in the act of constructing this delicate investment, but further investigation is necessary to confirm this supposition; it certainly seems somewhat inconsistent to find that while in every other member of the Family the fabricating organ is situated on the neural side, it should in this particular instance be placed on the opposite; but if their capacity as such be truly surmised, they certainly produce an effect differing essentially in the nature of the vagina so produced, which in this instance is more brittle than viscid.

While hastening for the press, I must conclude these observations with a cursory notice of the action of the marginal cilia, which, from the tardiness of their action in this particular Form, offer every opportunity for correctly appreciating their action, and of representing them on a drawing, though it is of course impossible

to convey the appearance of objects in motion; however impressive may be their appearance, the onward procession is but an optical illusion; I assume therefore that for the instant they are fixed when by the employment of linear projection the individual positions of the cilia are found to be as indicated on the drawing, which I submit is correctly represented, and shows more clearly and truly the actual appearance assumed in life.

II.-On an Improved Method of Photographing Histological Preparations by Sunlight.'

By J. J. WOODWARD, Assistant-Surgeon, U. S. Army. GENERAL: In January, 1870, I had the honour to submit to you a report in which I detailed the results of a series of experiments, which showed the superiority of the Electric and Magnesium lights over sunlight, as heretofore employed, for the production of photomicrographs of the soft tissues. In June of the same year I made a report in which I showed that similar results could be obtained with the Oxy-Calcium light. With these various artificial sources of light I obtained pictures which appeared to me to be "clearer and better defined than any photographs of similar objects I had hitherto seen produced by sunlight.'

So many cloudless days are offered to the photographer in Washington that I could not but regret these results; yet they appeared to be final at the time of writing. During the last few months, however, I have found improved methods of using the light of the sun for photographing the soft tissues, and have arrived at results which must materially modify the conclusions of my former reports.

Not that I have anything to withdraw from the opinions I have expressed, as to the certainty and success attending the use of artificial lights for the purpose named, but I have much to add with regard to the most advantageous methods of using the light of the sun for obtaining satisfactory pictures of tissue preparations, and such other objects as approximate them in optical characteristics.

If a well-made preparation, of some normal tissue, or of some pathological growth, stained with carmine, silver, or gold, and mounted temporarily in glycerine, or permanently in Canada balsam, be illuminated by white cloud illumination, or by lamplight, and found to be all that could be desired, it will nevertheless appear very unsatisfactory if illuminated by the direct rays of the sun.

The eye glancing through the tube of the instrument, dazzled by the powerful light, discerns amidst the blaze innumerable coloured

*The report is made to Brigadier-General J. K. Barnes, Surgeon-General U. S. Army.