protrudes into the septal tissue until it meets a cavity which communicates with the septal canal and with the anterior segment. Up to the present the author has not been able to detect any aperture at the extremity of this epidermic tube; but he is almost certain that such an aperture really exists, and may open under the action of certain muscular fibres. The septal canals, as stated above, are the way through which the eggs reach the fifth segment; but the fact that they exist in the second septum, whilst the segment in front of this has no gonad, shows obviously enough that they must have another function. The author ventures to offer the following explanation as to the function of all these well-guarded septal pores, and of the epidermic tubes of the fifth and sixth septa. It is a fact easily observed that the worm swells or dilates its body when it wants to adhere to the sheath in which it lives. And in this way it opposes such a powerful resistance, that it is quite impossible to pull it out of its tube without breaking its body in pieces; and when a part of the body has been cut off, the remaining segments do not relax at all, but remain as turgid and resisting as before. This shows that the various segments of the body may swell or relax quite separately. The septal organs are the valves which allow the coelomic fluid to flow in or out when they are open, but impose an insuperable resistance to its exit when the worm wants to dilate one or two segments separately. The paired tubes of the fifth and sixth septa are very likely intended to take in a small quantity of water from the outside, to be mixed with the coelomic fluid, when a larger quantity of it happens to be required. To sum up, although these researches and experiments are not finished, we have sufficient reason to consider the curious septal organs of Owenia as valves intended to regulate the pressure in the separate chambers of the perivisceral cavity, and to eventually divide entirely from one another those which at a given moment the animal desires to dilate under the contraction of the muscular coat of the skin. If this view is correct, we must regard the body of Owenia as a very elaborate hydraulic mechanism. 12. On a simple and efficient Collecting Reservoir for the Surface Tow-net. By W. GARSTANG. 13. On the Statistics of Wasps. By Professor F. Y. EDGEWORTH. The number of wasps in a nest may be inferred from the number issuing per minute if (1) we know the average time occupied by a wasp in the cycle of operations between two successive exits, (2) we assume that the whole population is occupied in keeping up the traffic. (1) The author has collected some statistics bearing on the first datum. The average time occupied by the wasps which he has observed in loading is six minutes-varying from two minutes, when the load consists of liquid sweets (of Sir J. Lubbock's observations), to ten minutes, when dried marmalade has to be hewed. The average interval between the departure of a laden wasp and the return of the same wasp for another load is with much less variation-nine minutes. Accordingly the mean periodic time for a wasp employed in collecting sweets may be assumed to be about fifteen minutes. This result is verified and corrected by other methods applicable to all kinds of employment-e.g., stopping the entrance of a small nest and noting the times of arrivals. The corrected figure is 20. If the number of wasps issuing per minute is X, the total number would be 20 x X, if assumption (2) held. But how inadequate it is is shown from the fact that the same nest within a short period shows very different rates of traffic. Thus a nest which at the beginning of a week had a traffic (entrances + exits) of twenty per minute, had, after three days, a traffic of sixty per minute; and, after two more days, a traffic of only twelve per minute, we can at best infer that the maximum observed rate of exit per minute, multiplied by 20, gives a minimum lower than the total number in the nest. In some cases examined by the author the minimum was found to be very much below the actual number. Thus a nest for which the observed maximum average rate of issue was eleven per minute, was found-when the whole population was killed and counted-to have contained, in round numbers, 600. A nest of which the maximum observed rate of issue was thirty per minute, was found to have contained 1,600. SATURDAY, SEPTEMBER 14. The Section did not meet. MONDAY, SEPTEMBER 16. The following Papers were read:— 1. On Insect Transformations. By Professor L. C. MIALI, F.R.S. 2. On Mounting Marine Animals as Transparent Lantern Slides. By H. C. SORBY, LL.D., F.R.S. For some years past the author has devoted much time to this subject, when on board the yacht Glimpse. The methods which give good results vary much in the case of different animals. Some must be arranged on the glass and dried quickly soon after having been caught, whereas others (like Medusa) must be treated over and over again with moderately strong alcohol to dissolve out all the salts. In some cases various staining materials must be used to bring out the structure, and some should be decalcified. Usually the animals are killed by keeping them for a short time in diluted alcohol, and are then arranged on the glass; and, after as much of the alcohol as will drain out is lost, they are dried in a current of air. The edges dry first, and so adhere to the glass that, on further drying, the animals become thin without any material change in form. In some cases they must be thoroughly soaked with clear gum before becoming quite dry. Finally, when quite dry, they are mounted in Canada balsam, and the edges of the cover glass very completely bound round so as to prevent the balsam running out when heated in the lantern. 3. Description of Methods for Collecting and Estimating the number of Small Animals in Sea Water. By H. C. SORBY, LL.D., F.R.S. The author described the methods he employs to collect moderately small animals by means of a brown holland bag, at the bottom of which is an arrangement so that brass wire sieves with meshes of various sizes can be fixed by a sort of bayonet joint. Through these the water flows readily, and the animals are easily washed off into a small bulk of water. Another method is to collect water in a special bottle at various depths from the surface to bottom, and to pour 2 gallons through a sieve having openings about bo of an inch in diameter. From this the animals are washed off into a few ounces of water. The numbers of the various kinds are afterwards counted in a small deep narrow trough filled over and over again until the whole quantity has been examined. The number of each kind per gallon can then be easily calculated. 4. On the Conditions affecting Bacterial Life in River Water. In a series of monthly observations, the author found that the microbes in the water of the Thames and Lea are, as a rule, much more numerous in winter than in summer. There are three conditions, to any one of which this difference might be attributed, namely, temperature, sunshine, and rainfall. By a series of graphic representations these three conditions are disentangled from each other by placing the results of the microbe determinations in juxtaposition with (1) the temperature of the water at the time the samples were taken; (2) the number of hours of sunshine on the day and up to the hour when the sample was drawn, and on the two preceding days; and (3) the flow of the Thames over Teddington Weir on the same day expressed in millions of gallons per twenty-four hours. Although the graphic representations were confined to the Thames, the conditions affecting bacterial life in this river are doubtless equally potent in other rivers and streams. These graphic representations afford definite evidence as to which of the three conditions just named has the predominant influence upon bacterial life in river water. They show that whilst coincidences between a high number of microbes and a low temperature and absence of sunshine are not wanting, some other condition entirely masks the effect, if any, of temperature and sunshine. This condition is the amount of rainfall higher up the river, or, in other words, the volume of water flowing along the river-bed. The interesting observations of Dr. Marshall Ward leave no doubt that sunlight is a powerful germicide; but it is obvious that its potency in this respect must be greatly diminished, if not entirely annulled, when the solar rays have passed through a stratum of water of even comparatively small thickness before they reach the living organisms; and the author shows, by a series of experiments upon the effect of sunlight upon the river water at various depths from the surface, that the germicidal effect of sunlight on Thames microbes is nil at depths of one foot and upwards from the surface of the water, even when the river is in a comparatively clear condition. It cannot, therefore, excite surprise that the effect of sunshine upon bacterial life in the great mass of Thames water should be nearly, if not quite, imperceptible. The author also calls attention to the powerful effect of storage reservoirs in the diminution of the number of microbes in river water, and to the very important bearing which this fact has upon the storage of flood water in the Thames Valley, for it leaves no doubt that storage for a month or two of the flood waters would effect such a bacterial improvement as would render the water of good quality for domestic use. By the construction of such storage works, the capacity of the Thames basin for the supply of good potable water to London would be enormously increased. 5. On the Exploration of the Islands of the Pacific. 6. On the Coccide of Ceylon. By E. E. GREEN. Since the publication of his papers on Lecanium viride and Chionaspis biclavis, the author has devoted three years to continuous work upon the Coccidæ of Ceylon. He has recorded 150 species, of which fully two-thirds were new, and found it necessary to create two or three new genera for the reception of strikingly aberrant forms. He referred to newly discovered organs in the encapsulated male, and remarked that he had in preparation a monograph, to be illustrated by 120 or more plates, giving figures of adults and larvæ drawn from life. On his return to Ceylon he contemplates continuing the investigation in both its scientific and economic aspects. 7. Criticisms on some points in the Summary of the Results of the 'Challenger' Expedition. By Dr. H. O. FORBES. 8. Observations on the Marine Fauna of Houtman's Abrolhos Islands, Western Australia. By W. SAVILLE-KENT, F.L.S., F.Z.S. Mr. Saville-Kent's investigations of the marine fauna of Houtman's Abrolhos Islands were associated with a visit he paid them in his capacity of Commissioner of Fisheries to the Western Australian Government, and were conducted with the particular object of advising that Government as to the conditions and prospects the adjacent waters presented for the establishment therein of profitable oyster or mother-of-pearl shell fisheries. Houtman's Rocks, or Houtman's Abrolhos, as they are variously charted, are so named after one of the early Dutch explorers in contradistinction to a coral group, also known as the Abrolhos, lying off the coast of Brazil. The island group discussed in this paper is a small archipelago, chiefly of coral origin, situated between the latitudes of 29° and 30° S., about thirty miles west of Champion Bay and the important Western Australian port of Geraldton. As a result of his investigations Mr. Saville-Kent found that the ordinary Australian rock oyster, Ostræa glomerata, occurred there in tolerable abundance and under conditions that would justify its being made the subject of systematic cultivation. The smaller West Australian variety mother-of-pearl shell allied to or identical with Meleagrina imbricata occurs very sparingly on the Abrolhos Reefs, but in the Commissioner of Fisheries' opinion was not worthy of serious attention in face of the unexpectedly favourable conditions he discovered to obtain there for the introduction and acclimatisation of the larger and more valuable species, Meleagrina margaritifera. This decision was arrived at as the outcome of an investigation of the associated marine fauna, and which was found to present features of high interest from both a utilitarian and a biological standpoint. The existing pearl and mother-of-pearl shell fisheries of Western Australia, as associated with the larger species, have not hitherto extended further south than Exmouth Gulf, in about lat. 22° S., and are consequently limited to the Tropics. The fishery for the smaller species, Meleagrina imbricata, is confined chiefly to Shark's Bay, three to four degrees south of Exmouth Gulf, and has in consequence of the wasteful depletion of the banks in former years been reduced to a comparatively low state of productiveness. Among other operations initiated by Mr. Saville-Kent, with the object of resuscitating the Shark's Bay fishery, has been the experimental transportation to it and cultivation of the large tropical pearl shell Meleagrina margaritifera. These acclimatisation experiments, although initiated only on a small scale, have been attended with complete success. The large mother-of-pearl shell has not only shown its capability of thriving in the colder waters of Shark's Bay, but has within a year of its transportation to this extratropical area commenced to freely propagate. The site selected for the foregoing experiments in Shark's Bay was the neighbourhood of extensive banks of coral growths pertaining to the genus Turbinaria. and from which reefs Mr. Saville-Kent obtained the remarkably large specimens of this Madrepore that are now on view in the exhibition galleries of the Natural History Museum, South Kensington. It has been determined by Mr. Saville-Kent in the course of his Australian explorations that the genus Turbinaria represents the group of Madrepores which in Australian waters enters most extensively into the composition of coral reefs in the colder or extra-tropical limit of their distribution. This predominance of Turbinarians had been found by him to obtain at Wide Bay, on the southern outskirts of the Great Barrier Reef in Queensland; in the colder though more northern waters at the head of the Gulf of Carpentaria ; and, finally, in the Shark's Bay district of Western Australia. The conditions which permitted the successful acclimatisation of Meleagrina margaritifera in Shark's Bay were found by Mr. Saville-Kent to be still more favourably fulfilled around Houtman's Abrolhos. In and among this island group, notwithstanding the fact that it lay some two degrees south of Shark's Bay, the character and composition of the coral reefs proved to be entirely distinct. In place of the extra-tropical Turbinariæ the corals of the Abrolhos Reefs comprise, as in essentially tropical districts, numerous varieties of branching Madreporæ, or so-called Stag's-horn corals, commingled with many species of Porites, Montipora, Pocillopora, Seriatopora, Coloria, Mussa, and other intra-tropical reef-building species. A yet more remarkable phenomenon, however, is recorded by Mr. Saville-Kent in connection with the marine fauna of Houtman's Abrolhos. This is the circumstance that he discovered on its reefs three of the most valuable economic species of Holothuridae or Bêche-de-mer, identical with types that are systematically collected in Torres Straits, and throughout the northern moiety of the Queensland Great Barrier Reef, but which are unknown to the coastal reefs of Western Australia further north, and where their place is taken by a distinct and much less valuable commercial species. The fish fauna of Houtman's Abrolhos, while corresponding to a large extent with that of the temperate Australian seaboard, as instanced by such genera as Pagrus, Aulopus, and Seriola, is also associated with many essentially tropical species, including, notably, a large assemblage of brilliantly coloured Labridae, or Parrot-fishes. Certain of these Labridæ, while not obtained by Mr. Saville-Kent in collections made among the mainland reefs of Western Australia, were familiar to him, as in the case of the Holothuridae, as denizens of Torres Straits and the northern region of the Great Barrier Reef. ocean The anomalous character of the marine fauna of Houtman's Abrolhos as herein defined can only be accounted for by the assumption that an current setting in from the equatorial area of the Indian Ocean penetrates as far south as this island group, and has borne with it the floating embryos of the Holothuridae and Coelenterates, &c., that so characteristically distinguish it. A reference to the Admiralty charts, dealing with the ocean currents of this region, supports this interpretation to a considerable extent; indicating, as a matter of fact, a prevailing northerly set along the western coast of Australia, but at the same time a distinct southerly intrusion of the waters of th Indian Ocean at some distance off shore down towards and closely approaching Houtman's Abrolhos. In further support of this interpretation Mr. Saville-Kent also determined by synchronous readings of the thermometer at the coldest season of the year, July, that as great a difference as from ten to fourteen degrees Fahrenheit distinguished the surface temperature of the sea at respectively the Abrolhos Islands and in Champion Bay. Mr. Saville-Kent remarks, in conclusion, that much scope is yet left for further investigation in this direction; while with respect to the anomalous character of the marine fauna it would be greatly to the advantage of marine biological science if a thoroughly exhaustive investigation thereof could be carried out. 9. On Hereditary Polydactylism. By Dr. GREGG Wilson. 10. On the Reproduction of the Common Crab. By Dr. GREGG WILSON. TUESDAY, SEPTEMBER 17. The following Papers were read: 1. Observations on Instinct in Young Birds. By Professor LLOYD MORGAN, F.G.S., Assoc.R.S.M. This paper dealt with observations on young moorhens, chicks, martins, and swallows with a view to determine how far the activities involved in locomotion |