Observations and Experiments on the Migrations of Filaria rhytipleurites, a Parasite of Cockroaches and Rats. By M. Osman Galet. On the Development of the Cephalo-thoracic portion of the Embryo of Vertebrates. By M. Cadiat. No. 3 (15th July) :— On the Spermatozoïds of the Cestoidea. By MR. Moniez. The Septicity of Putrefied Blood is lost by a very long contact with Oxygen compressed at high tension. By M. V. Feltz. The Structure of the Stem of Sigillaria. By M. Renault. No. 4 (22nd July): On the Theory of Fermentation. By M. Pasteur. Reply to the Communication of M. Pasteur. By M. Berthelot. By M. Max Cornu. On the Structure of the Sieve-like Tubes. By M. Ed. de Janczewski. No. 5 (29th July): New Communication on the subject of the Notes on Alcoholic Fermentation, found among the Papers of Cl. Bernard. By M. L. Pasteur. Observations of M. Berthelot consequent on the Communication of M. Pasteur. No. 6 (5th August): No Mycelium intervenes in the Formation and in the Normal Destruction of the Swellings developed under the Influence of the Phylloxera. By M. Max Cornu. On Prosopistoma punctifrons, Latr. By MM. E. Joly and A. Vayzzière. No. 7 (12th August): On the Functions of Leaves. Function of the Stomata in the Exhalation and Inhalation of Aqueous Vapours by Leaves. By M. Merget. On Parasitic Isopods of the Genus Entoniscus. By M. Alf. Giard. Importance of the Vegetable Cell-walls in the Phenomena of Nutrition. By M. Max Cornu. No. 8 (19th August): Experimental Researches on the Nervous Sudoral Fibres of the Cat. By M. A. Vulpian. Researches on the Nutrition of Insects. By M. L. Joulin. No. 9 (26th August): Comparison between the Salivary and Sudoriparous Glands, relatively to the way in which they are affected by Section of their Excito-secretory Nerves. By M. Vulpian. No. 10 (2nd September) : The Causes of the Buzzing of Insects. By M. J. Perez. The Application of Borax to Researches in Vegetable Physiology. By M. Schnetzler. No. 11 (9th September) : The Oviposition of the Queen-Bee, and the Theory of Dzierzon. By M. J. Perez. The Reproduction of the Hydra. By M. Korotneff. No. 12 (16th September): New Researches on the Physiology of the Vesicular Epithelium. By MM. P. Cazeneuve and Ch. Livon. No. 13 (23rd September) : On the Development of Chilostoman Bryozoa. By M. J. Barrois. No. 15 (7th October):— Note on a Memoir addressed to the Academy by M. J. Perez on the Buzzing of Insects. By M. Jousset de Bellesme. On Trichodonopsis paradoxa (Clap.). By M. A. Schneider. No. 16 (14th October): On a new Micrometer, intended especially for Meteorological Researches. By M. G. Govi. BULLETIN DE No. 12: LA SOCIÉTÉ BELGE DE MICROSCOPIE, Vol. IV., Proceedings of the Meeting of 26th September, 1878. The Malignant Tumours of the First and Second Childhood. By Dr. Ledeganck. (With 2 plates.) Analytical and Critical Review-of M. A. Renard's paper on "the Diabase of Challes near Stavelot,' in No. 8 of the 'Bulletin de l'Académic Royale des Sciences, Lettres et Beaux-Arts de Belgique,' and of No. 8 of the Zeitschrift für Mikroskopie.' Proceedings of the Annual General Meeting of 13th October, 1878, including the Report of the Council. General List of the Members of the Society. Academies, Societies, and Institutions with which the Society exchanges publications. Vol. V., No. 1. Proceedings of the Meeting of 31st October, 1878. 6 Report by M. Delogne on Dr. Matteo Lanzi's book The Thallus of the Diatomaceæ.' Analytical and Critical Review of M. Thoulet's paper on a "Process for measuring the solid angles of Microscopic Crystals," in the Bulletin de la Société Mineralogique de France,' 1878, No. 4, and of No. 9 of the Zeitschrift für Mikroskopie.' ZEITSCHRIFT FÜR MIKROSKOPIE, Vol. I., Part 9 (October): The Development and Present Position of Microscopy in Germany (conclusion). By Dr. Kaiser. On the Preparation and Preservation of Microscopic Aquatic Animals. Foreign Microscopes (continuation). By Dr. J. Pelletan. (From Journal de Micrographie.') A new Measurer for Covering-glass. On Washing and Cleaning Diatom-material. By C. Janisch. ZEITSCHRIFT FÜR WISSENSCHAFTLICHE ZOOLOGIE, Vol. XXXI., Parts 3 and 4 (issued 11th November): Contributions to the Anatomy of the Ophiuræ. By H. Ludwig. (With 4 plates and a woodcut.) On the Genital Organs of Asterina gibbosa. By H. Ludwig. Contributions to the Anatomy of Magelona. By W. C. 10 plates.) (With a plate.) McIntosh." (With (With a plate.) On some Cases of Parasitism in Infusoria. By I. van Rees. PROCEEDINGS OF THE SOCIETY. MEETING OF 13TH NOVEMBER, 1878, AT KING'S COLLEGE, STRAND, W.C. THE PRESIDENT (H. J. SLACK, ESQ.) IN THE CHAIR. The Minutes of the meeting of 9th October were read and confirmed, and were signed by the President. The following List of the Donations since the last meeting was submitted, and the thanks of the Society given to the donors. Annales des Sciences Naturelles (Zoologie). 1877) .. 14 vols. (1870 to (Botanique). 13 vols. (1869 to 1877). Henry, James. -Æneidea; or Critical, Exegetical, and Esthetical Remarks on the Eneis. 4 parts. 1873-8.. From Mr. Frank Crisp. Ditto. Author. Society. Author. Papers of the Eastbourne Natural History Society, 1877 and 1878 .. Zeitschrift für wissenschaftliche Zoologie. 10 vols. (1869 to 1877). Mr. Frank Crisp. A special vote of thanks was on the suggestion of the President given to Mr. Crisp for his valuable donations. Dr. G. W. Royston-Pigott, M.A., F.R.S., explained the leading points of a paper which he had sent to the Society, " On a further Inquiry into the Limits of Microscopic Vision, and the delusive The subject Application of Fraunhofer's Optical Law of Vision." was illustrated by numerous diagrams. (The paper will be printed in the next number of the Journal.) The President read a paper by himself, "On the Visibility and Optical Aspects of Hairs viewed from a Distance." (The paper will be found at p. 318.) Mr. Charles Brooke, in reply to a question from the President, On said that he thought the hair itself was not actually seen. the occasion when being illuminated by the sun-light a bright line was perceived at the great distance of 173 feet, he considered that the perception of it was due to an optical effect similar to that produced by the heating of a platinum wire by a current of electricity, when the wire apparently increased in thickness the hotter and brighter it became. Mr. Henry Davis said that the phenomenon was well known to astronomical observers under the name of irradiation, and it applied generally to all bright objects. Mr. Stewart inquired whether in the course of these experiments there was anything like " expectant attention" on the part of the persons concerned in them? Did they not know what they were to look for and exactly how they ought to see it, or were the hairs placed in positions vertically or otherwise without the persons knowing which way they were placed, so as to test whether they really did see them? The President said there was no attempt made to try the extreme distance at which the hairs could be seen, all the persons were required to do was to state a distance at which they could be distinctly seen. In one case the person did not know the position of the hairs; it was one of his men who had just come up from the village and did not know what they were about. In another case a person saw the horizontal hair, but failed to see the vertical one; and there was no endeavour made to ascertain who could see the objects at the greatest distance. One suggestion bearing upon the subject he thought might be a point for consideration, and that was that seeing the image of an object of 1 millionth of an inch in diameter might not be the same as seeing an object of that diameter. He had hoped to have seen Professor Stokes this evening, but he was engaged at Cambridge. Mr. Crisp said that as Professor Stokes had been referred to, it might not be without interest to read an extract from a letter referring to the subject, addressed by that gentleman to Mr. Mayall some time since: "As to Fraunhofer's formula, it is that which applies to the diffraction spectra formed by fine equidistant lines, and to that alone. The whole of the circumstances are so different from those, of the illumination and viewing of microscopic objects, that we have no right, I think, to draw any conclusion against the visibility of very fine objects, even though they be Nobert's lines, and therefore of the same nature as the object to which Fraunhofer's formula refers. In the Fraunhofer spectra the object is illuminated by nearly parallel rays, and the instrument is focussed for the distant slit, and the angular aperture is some 3° or 4° or less. When Nobert's lines are used as a test, the object is illuminated by strongly condensed light, the instrument is focussed for the lines themselves, and the angular aperture of the microscope objective is very much greater." He also read the following note from Mr. Mayall, which accompanied it : "In Arago's 'Astronomy' there are some curious remarks made on Photometry, which I think bear strongly on the question of the limit of visibility. Briefly this is the result at which Arago arrived :— If two adjacent points on a surface be unequally illuminated, the eye is capable of perceiving the difference when it is greater than ; a less difference than (or thereabouts) cannot be seen by the eye, and the two points will appear equally illuminated, and therefore not discernible as separated. "Applying this experiment to the microscope: suppose we have an anatomical preparation, unequally transparent, so that the most transparent part allows 61 rays to pass through, whereas the adjacent part allows only 60 rays to pass through; the eye still perceives the difference between them. But this is the limit (or thereabouts), otherwise the eye sees only a uniform surface. 60 "This difference of that follows from Arago's experiments as the limit of perception by the eye, is not an absolute quantity, but will depend somewhat on the sensitiveness in individual eyes. 66 'Again, too, it will depend on the intensity of the light in which the observation is made. There is necessarily a particular intensity the most favourable to enable us to distinguish these small differences. "If we look at the sun with the naked eye, we do not see the spots, although from their size they should be seen. If we take a smoked glass we see them at once. With too dark a glass they disappear, although we may still see the disk of the sun. This phenomenon takes place with the microscope when the illumination is too brilliant or not sufficiently so." The President said that Dr. Pigott, after the meeting, would exhibit his apparatus to the Fellows. Mr. F. H. Wenham read a paper 66 On the Measurement of the Angle of Aperture of Objectives," illustrating the subject by a diagram, enlarged upon the black-board by Mr. Stewart. Mr. Wenham also said that Mr. H. Davis, who was present, had seen the operation of measurement, and would vouch for the fact that it was a very simple affair. (Mr. Wenham's paper will be found at p. 321.) Mr. Henry Davis gave some extracts from a paper he was about to present "On the Pygidium of Insects," illustrating his observations by drawings on the black-board. (The paper will be printed in the next number of the Journal.) Mr. Charles Stewart thought that the term pygidium was merely the name given to a particular tergal plate of the posterior part of the abdomen, upon which, in the case of the flea, these curious hairs were found. He believed that somewhat similar hairs had been described by Dr. Braxted Hicks and others, as occurring on other parts of the bodies of insects. He only wished to ask, as a matter of information, whether the term was applied to the hairs, or whether it belonged to the particular part upon which they were ordinarily found? The circi, as these things had been called to which Mr. Davis drew attention, were really a pair of upstanding bodies, and were each divided into twelve little pieces; they were not at all unlike posterior antennæ, and he thought they would hardly come within the description of pygidia, although they might bear similar hairs, and perform a like function. Mr. Davis said that the term had always been applied to the organ itself in the case of the lace-wing fly, and therefore he had from its analogy applied it to the organs of other insects; but if it was wrong to apply it to the fly, then it was wrong to apply it to the others. On the other hand, however, if this organ in the lace-wing fly was a pygidium, then that of the locust was certainly a pygidium also. In some of the species of cockroach, the same thing was found starting from the same place, but only carried out a little longer. As regarded the cockroach (Blatta), it might at first be thought that the thing was not the same, but he felt sure that if anyone went through them carefully and traced them out by their analogies, there would be no difficulty in showing that they were really the same. Mr. Stewart said that if he recollected rightly, at the posterior end of |