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named Melicerta tubicolaria; as I have now little doubt, in spite of the errors in his figures and description, that this was the rotifer out of which Ehrenberg framed his genus Tubicolaria.
Nothing can be more irregular than the shapes of the homes in which these creatures dwell. They are fluffy masses of a substance secreted by the animal itself, and fortified by random gatherings of material thrown down on them by the action of the ciliary disk. Like those of all the tube-making rotifers, they have only a small cylindrical passage down their centre, up and down which the animal moves, and the material of which they are composed is continuous from the rotifer right out to the surface. By transmitted light they appear to be hollow; but this is not the case, and the dark-field 'illumination will generally enable the observer to trace the delicate material everywhere from the outer surface to the animal within. In Floscularia campanulata I have seen the young newly-hatched male bore his way with his long cilia from the side of his mother right out of her case ; and I have also seen it die in the attempt. The most remarkable thing about cistes umbella is its disk, which is so strengthened by ribs across it in various directions, that it looks somewhat like an odd kind of umbrella. Two of these thickenings are very broad, and run across, as shown in the figure, from the ventral to the dorsal side of the disk. When the rotifer closes its disk, it naturally folds it so as to bring these stouter portions together, the thinner parts being folded within them; and, in consequence, it often has an odd square look about its head, that I have never seen in any other species of Ecistes. But this strengthening of the disk is not peculiar to it. The common Ecistes crystallinus has precisely the same thing, only on a much smaller scale (as may be seen in the Plate, Fig. 3), and similar thickenings are visible in E. pilula.
In €. umbella there is on either side of the disk a branched rib like a gusset; but the whole structure must be viewed in various directions and by different modes of illumination to get a clear idea of it. The central ribs, when the disk is viewed edgeways, are clearly seen to project above its surface a little.
My friend Mr. A. W. Wills found this rotifer in one of the ponds of Sutton Park, and exhibited some specimens in October at à meeting of the Birmingham Natural History Society.
Mr. Wills has figured and described it in the December number of the
Midland Naturalist,' adding to his interesting remarks some accurate measurements of a full-grown individual. From these it will be seen that E. umbella is much larger than E. crystallinus, and about twice as large as E. pilula. On a piece of alga which Mr. Wills has just sent me, the two species can be seen side by side, and form a very pretty picture. They have been living in Mr. Wills' tank, and have come to me in excellent condition in
spite of the severe weather, which seems to have killed all their brethren in the ponds.
E. umbella has two well-marked red eyes which can be seen on looking down through the disk; they are situated well within the animal, below the disk, and towards the dorsal side, that is, towards the side where the mouth is not.
Ehrenberg's family, Ecistina, ought of course to be included in the family of the Melicertans, but I agree with Mr. Wills that the genus cistes ought to be retained, as we have now no less than five species ; viz. E. crystallinus ; Mr. Davis' new pair, E. intermedius and E. longicornis ; Mr. Tatem's E. pilula ; and Mr. Oxley's E. umbella.
Conochilus volvox.— I had the pleasure of reading Mr. Davis excellent paper on this most curious rotifer," just after I bad been drawing it from a few specimens which had survived the transit from London to Clifton. The creature is a bad traveller, , not a single sphere remained unbroken ; and indeed the tube contained no group with more than four rotifers in the cluster. In some respects this was an advantage, as it enabled me to see much more clearly than I otherwise should have done the animal's structure. First let me say that Mr. Davis' account of this rotifer is most accurate. He is quite right in pointing out that there are the usual pair of setæ-bearing antennæ, one on either side of the mouth, not four conical papillæ, each with a bristle, as Ehrenberg asserts. He correctly states that the line of cilia is interrupted in one part of the disk, and that the notch in the cilia is not where the mouth is. Mr. Davis has also most clearly shown the peculiarity of this rotifer’s structure in having its mouth and anal aperture on the same side: and in its fringe of large cilia enclosing that of the small cilia as well as the mouth; instead of its being enclosed by the smaller cilia, and of the mouth's lying between the two fringes. Mr. F. A. Bedwell has given an admirable and most forcible illustration of the difference between the trochal disk of Conochilus and that of Melicerta in his capital paper on the building apparatus of Melicerta ringens.
The arrangement of the parts is so curious in Conochilus, and 80 exasperating to a classifier, that I may venture to suggest even a third way of considering them. If a crochet hook were supposed to be pushed through the centre of the disk, down the middle line of the body, and hooked on to the end of the foot, then on drawing the hook right back again, the animal would be turned inside out like the inverted finger of a glove, and be pulled through its own disk; and the relative position of its organs would be nearly that of
ordinary Melicertan. In the drawing that I have given of a Conochilus, it will be seen that the anal aperture lies remarkably * .M. M. J.,' vol. xvi. p. 1.
high on the back, and that it has a curious trefoil opening. In one of the specimens I could distinctly see several spermatozoa attached to the ovary and still moving. The spermatozoa were of two shapes—or at all events along with the usual spindle-like forms were others like a curved cord with a puckered ribbon sewn all down it. Both these forms can be readily seen in the sperm sacs of the males, and both are constantly in motion. How the spermatozoa got outside of the ovary I cannot imagine—and that some were outside I am certain. The ovary, I believe, opens into the anus, and I know of no way in which the spermatozoa could escape into the perivisceral cavity.
There is a point of resemblance between Conochilus and the Floscules which is well worth notice. From the mastax to the mouth the alimentary canal is strengthened in an unusual way by a tube much harder than the surrounding parts. In Floscularia campanulata the tube hangs down from the mouth, and is constantly thrown into long slow undulations. As it is transparent, its edges only can be usually brought into focus, so that it looks like two waving lines or like the edges of two flat membranes, and thus it has been described. Under favourable circumstances, however, food or water may be seen to dilate it as it passes down, and I have repeatedly seen this happen in such a way as to make it obvious that the structure is really a tube. On crushing F. campanulata or Conochilus volvox, the tube will be found to remain, and even to resist the action of caustic potash along with the harder portions of the mastax.
Notommata aurita.--A few months ago I found this rotifer in great abundance in a pond near Bath. The water was swarming at the same time with free Vorticellæ of a fine dark green, speckled with brown. The bottle that I carried home with me had a very large number of these restless creatures in it, and I found them very much in my way as I was examining the Notommata, for they constantly knocked up against the rotifers, and made them withdraw the curious earlike appendages from which they derive their name, and which I was anxious to see. One thing puzzled me very much, and that was the rapid disappearance of the Vorticellæ from the bottle. The surface of the water was alive with them when I brought them home, and next morning there were not a fourth of the number to be seen. Almost all the Notommata, too, were useless for purposes of observation, for they were gorged with green food, so that their stomachs hid the other organs. The exact similarity of tint between the contents of the Vorticella and the stomachs of the Notommata had already struck my attention, when I thought I saw a rotifer (unluckily on the opposite side of a bit of horn-wort) holding one of the Vorticellæ. Could it be possible that these Notommata could eat the Vorticellæ ? I put a large
piece of the weed, in which several specimens of both creatures were entangled, under the Microscope, and with a low power watched eagerly to see if I could catch the rotifer in the fact. After a few minutes' observation, I was inclined to reject the idea as absurd.
The Vorticellæ rushed backwards and forwards, knocked fearlessly against the rotifers, and, while evidently frightening the latter, took no sort of pains to get out of their way ; in fact, behaved, as to me they always do seem to behave, just like animated machines. As to the slow-swimming and still slower crawling rotifer catching one of these swift rovers, the thing seemed impossible. Under any circumstances, whether swimming or crawling, whenever the Vorticella struck the Notommata, the latter either drew in his wheels, and ignominiously rolled over and over to the bottom, or if it were crawling on a bit of the weed it shrunk back, and contracted itself with every appearance of alarm.
Still there were two ugly facts unaccounted for, viz. the disappearance of the Vorticellæ, and the appearance in the stomachs of the Notommata of substance marvellously like them. I was just going to try to imprison a Notommata in a coil of cotton with one or two of the Vorticellæ, when I noticed one of the latter caught in the angle between two small stems of horn-wort. A Notommata, too, was crawling along one of the stems in its usual slow fashion. There was a chance that the sluggish creeper might get to the angle before the Vorticella darted off again on its travels. Fortune favoured me; the Vorticella kept waltzing round and round in the same spot, and the Notommata crawled on till it all but touched the Vorticella. I hoped to see the rotifer quicken its pace, or make-I will not say a dart, that would be too much, but at all events a lurch at its prey; imagine my chagrin when I saw it coolly curl round the stem and begin to retrace its steps, actually freeing the Vorticella from its prison by brushing it with its back as it crawled back again. There had not been a thousandth of an inch separating the rotifer's head from the Vorticella, and yet, in spite of its two eyes, it had not noticed it. Again, I thought of bringing in a verdict of “not guilty”; but another good look at dark green stomachs revived all my suspicions, and once more 1 patiently waited till another Vorticella, possibly the same, repeated its silly performance of getting into a corner and dancing there till some one should set it free. This time it was freed only too effectually. The Notommata once more crawled down to the captive, “without hurry or care," and struck its nose (if I may use the expression) against the Vorticella, just as if it were by accident. But the instant it did so it jerked up its head, and snapped at and seized its victim with its sharp jaws; and in a second I saw the whole contents of the Vorticella pouring down the throat into the stomach of the rotifer. Guilty !_and without appeal.
There are a few observations showing that the rotifers occasionally use their maxillæ as teeth, but only a few. Mr. Gosse mentions the snapping action of those of Synchæta mordax. Mr. Slack saw a Diglena chase, seize with its jaws, and shake an anguillula that had presumed to jostle it. I have frequently seen Hydatina senta protrude its maxillæ, and snatch at some tempting green globule that the cilia could not quite force down the mouth; and once I saw a small Notommata deliberately snip the side of the cell of an alga, and suck out its green contents. On this occasion I contrived to see the catching of Vorticellæ by Notommata several times, and in each case the Vorticella was seized by the rotifer's maxilla and its contents so completely appropriated that it was hardly possible to see the delicate film that was left after the operation had taken place.
Melicerta ringens. - Mr. F. A. Bedwell has given a most interesting and suggestive account of the building apparatus of this rotifer, in the November number of the Monthly Microscopical Journal' for 1877.* His description of the various currents which pass round and through this apparatus is admirable. To one point alone do I feel inclined to take any exception, and that is, to the separation of the particles into “four deflected streams” by the action of a sensitive cushion above the mastax. I quite agree with Mr. Bedwell that a first selection among the particles whirled round the groove of the disk is made by “two knotty protuberances set symmetrically one against the other” just at the ends of the collecting groove, and directly opposite to the chin; and that from these the main stream of waste material is directed in a great rush over the chin. But I think that the very feeble currents which creep along (as Mr. Bedwell has so well described) under the curved edges of his "hopper” admit at least of another explanation. If Melicerta ringens is fed with carmine, and the chin and its appendages steadily watched, it will be seen that on either side of the swift main stream which carries the waste particles over the chin, runs a feeble current between it and (if I may use the term) the bank ; running, in fact, as already said, under the curved edges of Mr. Bedwell's “hopper,” and along what Mr. Cubitt calls the “chases.” In these currents are gently carried along such minute particles as are fitted to form the pellet, and they pass over the two notches at the chin into the pellet cup. About these facts I think there can be no doubt. It is the modus operandi only that is in question. It is of course possible that the sensitive cushion described by Mr. Bedwell may, like a skilful batsman, strike the larger particles into the centre of the stream, and the smaller ones to the sides where
* "M. M. J.,' vol. xviii. p. 214.