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In one species I found three or four isolated ones in the centre of the dorsal surface of each fin.

In section it is seen that each organ is a spheroidal body embedded in the subcutaneous cellular tissue, and consisting of the following parts: (1) an outer pigmented cup with a considerable aperture (a quarter of its circumference) in front. (2) A lining within the cup, consisting of a single layer of cuboidal cells, with spherical nuclei, easily stained. (3) The anterior aperture of the pigment cup is filled by a lenticular body, composed of masses of a structureless yellowish material, to all appearance cuticular in nature, with small deeply-stained cells between the masses. (4) From the back of the lens there projects into the centre of the organ a conical plug, composed of deeply-stained cells. These are seen in transverse sections to be disposed concentrically round the axis of the cone, producing the effect of the well-known 'cell nests' of an epithelioma. (5) The space between this plug and the cells lining the pigment cup is filled with a clear transparent mass. In its peripheral portions this seems to be made up of thin layers arranged concentrically like the coats of an onion; whilst nearer the centre it has the form of curved rods, wider in front than behind, amongst which nuclei are sparsely scattered.

In most cases a space, most likely a blood lacuna, was seen around the organ; no nerve supply could be traced out.

It is impossible without an opportunity of examining the living animal to say what part of this apparatus is the active agent in producing the light; indeed, it must be remembered that positive proof of its being a luminous organ at all is still wanting.

Of similar structures as yet described in other animals it seems to resemble most nearly the photospheria of Nyctiphanes norvegica, a schizopod crustacean examined by Messrs. Vallentine and Cunningham. As regards origin, these organs are probably to be regarded as highly modified chromatophores; an analogous modification would be found in the thermoscopic spots recently described by Joubin in another cephalopod.

2. Report on the Marine Zoology of the Irish Sea.-See Reports, p. 526.

3. Interim Report on a Deep-sea Tow-net.

4. The Origin of Organic Colour. By F. T. MOTT, F.R.G.S.

In a complete plant of the higher orders there are three distinct schemes of colour-viz., the browns, olives, and maroons of the stem and branches, the greens of the foliage, and the reds, yellows, and blues of the blossom.

These indicate a successive decrease in the amount of light absorbed, which must be the result of changes in the absorbing capacity of the molecules. It is suggested that the cause of these changes may be found in the specially organic phenomenon of food assimilation, and the concentration of energy in the molecular structure which this implies. If such energy is stored in the form of increased molecular vibration, sets of molecules will successively reach the maximum limit of vibration possible to them, and will lose the power of further absorption. Thus the amount of reflected light will increase as the plant attains maturity; and as the arrest of growth which accompanies the formation of blossom throws upon the vibration of the molecules the energy otherwise expended upon growth, a marked increase of reflected light from the flower is the natural result.

5. Remarks on the Roots of the Lemna and the Reversing of the Fronds in Lemna trisulca. By NINA F. LAYARD.

The roots of the various English Lemnæ are usually described as identical in form and structure, if, indeed, they receive any attention at all; but a careful

comparison of their forms will show certain distinct, albeit slight, differences, sufficiently marked to make it possible to identify a plant by means of the root alone.

One of the objects of this paper was to point out those differences by means of diagrams in which the respective roots of Lemna minor, trisulca, gibba, and polyrhiza were represented side by side.

Besides a considerable variety in the length of the various root-fibres, a microscopic examination of the sheaths which protect the apex shows that neither are they uniform in shape, but, ranging from the comparatively blunt and straight ampulla of Lemna minor to the slightly pointed sheath of Lemna gibba, they become blade-like in Lemna polyrhiza, and, finally, sharply pointed and with a tendency to curve in Lemna trisulca.

As the plant matures the sheath becomes a ruddy brown colour, and is seen under the microscope to be freckled with brown blotches, probably the decaying outer cells of the case. This hardening of the ampulla is a very necessary security against the attacks of water insects, which feed upon the delicate root fibres, often commencing at the extremity of the root and working their way upwards.

It is interesting to speculate as to possible other uses for this rather phenomenal root-cap. The functions of the root-caps of terrestrial plants are easily recognised in their adaptability to the purpose of forcing a way for the fibre through soil or pebbles, but here we have plants suspended in the water, and yet furnished with something very similar. This difficulty has been met by the suggestion that the sheath of the Lemna is not a root-cap, but really a persistent digestive pouch; but, even without this explanation, one has only to take into consideration the characteristics of the habitat of the duckweed to see that the ampulla is continually required to do the work of any ordinary root-cap of terrestrial plants. Owing to the stagnant nature of the ponds and dykes where it flourishes the plant is subjected to violent alternations of drought and plenty, and in the dry season myriads of perishing Lemnæ are left high and dry on the banks. The more fortunate individuals, growing where the water is deeper, are gradually let down as it becomes more shallow, until at last, striking their roots on the soil at the bottom, they are embedded in the mire, and there await the return of rain.

A curious hooked appearance which is occasionally seen in the ampulla of Lemna trisulca was also represented in the diagrams.

In the long chains formed by a number of connected fronds of Lemna trisulca it will not infrequently be found that the root-fibres spring sometimes from below the frond and hang downwards, and sometimes from what appears to be the surface of the frond, reaching upwards. A careful observation of the tendency of this submerged duckweed under certain circumstances to twist into an almost spiral form led the author to the conclusion that in such cases the fronds had completely revolved in their sockets, so that what had at first been underneath was now uppermost, throwing the root attached to it up to the surface. Further observations seemed to point to the fact that this habit is confined to cases where the submerged Lemna trisulca is covered from light and air by a thick overgrowth of other weeds, such as Lemna minor, with which it is often associated; for in a pond where this was not the case the uncovered chains of Lemna trisulca were lying almost flat, but after being placed in a basin already containing Lemna minor they also assumed an irregular spiral form in the course of a few weeks. Should this change be found to be attributable to a want of air it may possibly point to a respiratory function in the root-fibre.

SATURDAY, SEPTEMBER 16.

The following Reports and Papers were read :—

1. Interim Report on the Botanical Laboratory at Peradeniya, Ceylon.

2. Interim Report on the Legislative Protection of Wild Birds' Eggs. See Reports, p. 552.

3. On the Etiology and Life-history of some Vegetal Galls and their Inhabitants. By G. B. ROTHERA.

In the restricted sense in which the term is here applied, galls are defined as complex organisms resulting from the co-operation of a plant and an animal; and to determine the extent and modus operandi of these two factors in their production is one of the many interesting problems which this study presents. Though abnormal with regard to the plant, inasmuch as their presence is exceptional and foreign to the performance of its proper functions, galls are in themselves as normal as any other organisms. Each has its own characteristic form, its special habitat, and its proper office. Hence, after referring to the great diversity of these organisms and their wide distribution, the writer proceeds to trace out the lifehistory of certain typical galls, those of Cynips Kollari, Teras terminalis, and Biorhiza aptera being specially dealt with.

What is there, he asks, in the casual presence of the ovum of the gall-producing insect, in the action of the developing larva, in the mechanical puncture of the parent cynips, or in the deposit of a tiny drop of irritating fluid by which it is said the ovipositing is accompanied what is there in any one, or more, or all of these, or, it may be, in the action of some other factor yet to be discovered, that impels these wonder-working changes by which the gall itself is initiated and its future growth and development accompanied? Reviewing the various attempts made to answer this and cognate questions, as also the arguments by which the generally accepted view of the deposit by the parent cynips of a special virus is supported, the author denies the alleged analogy upon which the conclusion thence arrived at rests. The presence of the ovum (not found in any of the cases stated) may be, he suggests, as necessary a factor in the production of the gall as is the deposit of a specific virus; while in many cases galls are found to result from the action of other animals than terebrant hymenoptera-as, for example, of kermes, cecydomia, and acari-where no such poison-gland as that referred to exists. Very early in his investigations (now extending over a period of five-and-twenty years) the writer arrived at the conclusion that another agent, as potent as that of this hypothetical virus, was essential to the production of, at least, some species of vegetal galls, such agent being the presence and action of a living larva. In illustration of this the 'oak-apple' may be taken. Here the parent cynips (Biorhiza aptera— the agamic form of Terasterminalis), by a dexterous use of her terebra preparatory to ovipositing, makes a cut across the axis of a winter bud of the oak, above the circlet of scales by which it is surrounded, so as to separate the cone-like apex with its appendages. In the space thus prepared a variable number of eggs is laid at times as many as two hundred and fifty or more. Should these, however, notwithstanding the incision, fail to be deposited, or, if laid, perish during the winter, no growth, normal or abnormal, takes place from the divided axis. This remains brown, dry, and inactive. If, on the other hand, healthy ova are present, and these hatch out their living embryos, then, by the action of these upon the dormant tissues, new and peculiar powers of growth are manifested— powers which result in the production, not of a normal branch, but of an abnormal, tumour-like gall. Here, then, we have a series of facts, positive and negative, which point to the action of the embryo, and not to the deposit of a special virus by the parent cynips, as the direct and necessary agent in the production of the gall. Granting, for the sake of illustration, the existence and potency of such virus, ought we not in such case to expect that, even in the absence of living larvæ, the normal energies of the fluid would be exerted, and a gall, destitute though it might be of normal occupants, of necessity result? In the author's long experience no facts confirmatory of this view have been met with, nor is it probable that any such barren galls exist. Are we not, then, justified in discarding the hypothesis of 'Published in extenso in Natural Science, November 1893.

a specific virus deposited by the parent cynips, and in attributing to the activities of the living embryos, combined with the normal forces of the plant, the genesis and metamorphoses of the gall?

This view has since been emphasised by Dr. Beyerinck, of Utrecht, who, as a deduction from the same facts, holds that in the action of the cynipidæ larvæ, and not in the injection of a specific virus by the parent cynips, the cause of gall formation is solely to be found. Whether so or not, however, this, at least, may safely be concluded, namely, that while, on the one hand, in those chemical and other forces which produce growth greater activity is induced by the stimulus of the injected fluid-assuming this to be actually present-so, on the other, those mechanical conditions which determine form in organic beings are furnished to a large extent by the contact of the included ovum and by the activities of the embryonic larva.

Resting in this solution of the problem, the author proceeds to deal with the facts of parthenogenesis and metagenesis, as exhibited in the gall-producing cynipida, and then to trace the operations of phytophagous and entomophagous inquilines and parasites,

'The unbidden crew of graceless guests' (Virgil),

which, season by season, decimate the cynips' larvæ, the legitimate possessors of the gall, living on their fatty juices, or so robbing them of their food that they die of poverty and inanition. But here, again, as if to punish wrong and work retributive justice, these inquiline and parasitic enemies in turn are preyed upon by other parasites lower in the scale of creation than themselves, which thin their ranks, and thus, in a rude and barbarous way, maintain the necessary balance of organic life.

4. On some New Features in Nuclear Division in Lilium martagon. By Professor J. B. FARMER.

A careful examination of the course of development of the pollen in Lilium martagon shows the presence of a varying number of bodies which seem to have escaped the observation of those who have hitherto investigated this plant. To these bodies the general term 'granule' has been given, as one which involves no assumption as to their real nature. These granules are not easily made clear except by the careful use of selective stains. One of the best methods, though by no means the only one, of sharply differentiating them is that of double staining with hæmatoxylin and orange G. The great importance of the granules lies in the fact that a variable number of them may become converging points for the achromatic spindle fibres, and the whole spindle thus becomes multipolar and irregular. This does not, at any rate in the earlier stages of karyokinesis, terminate in any definite granule which may be regarded as a centrosome.' This behaviour on the part of the granules obviously affects deeply the whole question of the individuality of the centrosome.

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As to the origin of the granules, it is of extreme interest to find that they appear suddenly in the cytoplasm, which had hitherto been perfectly free from them. Their appearance is immediately subsequent to the fragmentation of the large nucleolus during the preparatory stages of division, and moreover in their staining reactions they exactly coincide with those presented by this structure. A possible connection between the nucleolus and the granules is thus indicated.

During the later period of division the granules become fewer and larger, but their ultimate fate is not as yet quite clear.

The above points were illustrated by photomicrographs.

MONDAY, SEPTEMBER 18.

The following Papers and Reports were read :

1. On Coral Reefs. By W. J. SOLLAS, M.A., F.R.S.

A discussion on Coral Reefs was opened by the reading of this Paper.

2. Report on Work carried on at the Zoological Station, Naples.
See Reports, p. 537.

3. Report on Work carried on at the Biological Station, Plymouth.
See Reports, p. 546.

4. Interim Report on the Index Generum et Specierum Animalium. See Reports, p. 553.

5. A few Notes on Seals and Whales seen during the Voyage to the Antarctic, 1892-93. By WM. S. BRUCE.

During the recent Antarctic cruise at least three kinds of seals were seen. These were all true seals; no fur seals were seen. They were the sea-leopard (Stenorhynchus leptonyx), Weddell's false sea-leopard (Leptonyx Weddellii), and a creamy-white seal, probably the crab-eating seal (Lobodon carcinophaga). There were two others, which were possibly younger forms of sea-leopard and crab-eating seals respectively. The latter, instead of being white, was mottled pale grey, but similar in form and size to, and often found among, the white seals. In December all the seals were in very bad condition, thinly blubbered and grievously scarred. The females were scarred as freely as the males. There was no marked preponderance in the number of the females. During January their condition improved, and by February they were heavily blubbered and free from scars. Loving the sun, they lie on the pack ice all day digesting their meal of the previous night, which consists chiefly of fish or small crustaceans, or both; the penguin is also occasionally their victim, and I have found stones in their stomachs.

By February the embryo is well developed, gestation probably beginning in December. It is extremely regrettable that it was during this period the indiscriminate slaughter took place, almost all the females towards the end of January and February being with young.

All the seals were found on the pack ice; the sea-leopard was on the outermost streams, and was most frequently to be found singly, though two or three might be on one piece of ice, but seldom more. Weddell's false sea-leopard was very rare, only four of them having been seen. The creamy-white seal and the pale mottled grey were in greatest abundance: these are found in fours, fives, or even tens-the greatest number I have seen on one piece was forty-seven. On one occasion we found some seals on a tilted berg; so high was the ledge above the water-level that our men with difficulty clambered up and secured their prey. This illustrates their great power of jumping from the water on to the ice. I have seen them rising about 9 feet above water, and cover distances of fully 20 feet in length.

It is of interest to note that we saw no trace of any whale resembling the bowhead or Greenland black whale (Balæna mysticetus) which Ross reported to have seen in very great numbers. There were, however, hunchbacks, finbacks, bottlenoses, and grampuses.

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