Glyciphagus plumiger. In 'Science-Gossip' for July, Mr. A. Michael mentions the capture by him of this acarus in England, in fodder in a stable. Though only one other case of its capture here is on record, Mr. Michael considers that from the fact of it having been found in two remote parts of the country, between which there would not be likely to be communication, and which are both agricultural, it may be fairly claimed as a British species, although only a single individual has been detected in each instance. A woodcut of the female (not previously figured) is given.

A New Family of Calcareous Sponges.-Mr. H. J. Carter describes, in the Annals' for July, two new species of calcareous sponges, in which the excretory canal-systems do not open into a common cavity (the "cloaca" of Dr. Bowerbank) which discharges itself at one or more apertures, but open directly upon the surface.

Mr. Carter gives the following description of the single genus of the family :

Teichonellida (Teîxos, a wall), new family. Character.—Vallate.

TEICHONELLA, Nov. gen.

Generic characters. · Vallate or foliate, without cloaca. Vents numerous, confined to the margin, or general on one side of the lamina only; naked.

Both the species T. prolifera and T. labyrinthica (which are described at length and illustrated in a plate of nine figures) are in the British Museum-the former (which is by far the largest Calcisponge on record) for many years and the latter (only second to it) were in Dr. Bowerbank's collection purchased by the Museum. Referring to Professor Haeckel, Mr. Carter considers it "somewhat laughable that the self-constituted author of 'The History of Creation' should have omitted a whole family of the Calcispongia."

The Polarizing Microscope in Mineralogy.-At the session of 4th February last of the French Academy of Sciences, a note by M. A. Michel Levy was presented by M. Des Cloizeaux, on the use of the polarizing microscope with parallel light for the determination of the species of minerals found in thin plates of eruptive rocks, by means of the depolarizing axes which the crystallized elements of these minerals evince in parallel light between two crossed Nicols.

The crystallographic orientation of these elements is generally indeterminate, and the employment of the polarizing microscope with parallel light is alone possible on account of the minuteness of the crystals and the extreme tenuity which must be given to the plate to render it sufficiently transparent. But these inconveniences are compensated by the large number of crystals which can be operated upon, and by the elongation which certain species assume in a particular direction.

M. Levy proposed to study the variations in the position of the depolarizing axes of a given mineral with respect to the different sections which were produced parallel to its edge of elongation, by finding the angle of each position of the depolarizing axis with that

edge, the direction of the same being constant. In fact, the sections belonging to this zone may generally be distinguished at the first glance in a thin plate, and they strike the eye by their characteristic elongation and the known relation of this elongation to the facile sections.

M. Levy has determined under these conditions the angles of the depolarizing axes of pyroxene, diallage, amphibole, epidote, sphene, and orthoclase, and has determined in triclinic feldspars that some specimens belong to oligoclase and some to labradorite.

The Radiolaria.-To all who are interested in this group may be commended the perusal of Mr. St. George Mivart's paper, which is printed in No. 74 of the Linnean Society's Journal' (Zoology). The paper, though headed "Notes touching Recent Researches on the Radiolaria," is in reality a condensed treatise on the group; and, whilst constituting somewhat of an innovation upon the usual practice of learned Societies, will be generally thought to establish a valuable precedent, and one that might be very usefully followed with other subjects and in other Societies, particularly where, as is the case with the Radiolaria, the results of their investigation are for the most part locked up in a foreign language. Mr. Mivart thus prefaces the paper :-‘ "The example which has been set by our President in publishing from time to time in his successive addresses a digest and résumé of the most recent researches which have been carried on respecting certain of the lowest animal groups, has led me to believe that a similar course might advantageously be taken with respect to the Radiolaria. Our publications already afford, through Dr. Allman's recent labours, the readiest means of obtaining a knowledge of the most modern investigations with respect to various groups of Protozoa, and I have myself found the memoirs referred to most valuable and useful. I hope that other Fellows may adopt a similar course, so that our journal may become a complete repertory of information respecting all the lower groups of the animal kingdom. No English publication on the Radiolaria exists to my knowledge, and, although the most admirable monograph of Professor Haeckel was at the time (1862) a complete and exhaustive account, yet were it even readily and generally accessible, important additions have now been made to our knowledge of these animals since its publication. I venture to think therefore that an account of these beautiful, and in many respects complex organisms, will not be an unwelcome addition to English zoological literature."

The paper commences with a general descriptive account of the Radiolaria, followed by observations on their impressionability, locomotion, and nutrition; reproduction and growth; zoospores (with and without crystals); modes of growth; distribution; classification, and literature.

In concluding the descriptive part of his subject, the author says that "to his mind it seems evident that these beautiful symmetrical and complex forms cannot be due to the action of natural selection, and sexual selection can of course take no part in forming such organisms as these. We seem here to have forced upon our notice the action of

a kind of organic crystallization, the expression of some as yet unknown law of animal organization here acting untrammelled by adaptive modifications or by those needs which seem to be so readily responded to by the wonderful plasticity of the animal world."

The multicellular nature of Radiolarians, it is pointed out, now depends entirely on the normal nature of their yellow cells, and on the correctness of the observations as to the centripetal cell-groups of Physematium. Neither of these phenomena can be reposed on as being certainly of the nature of true cells forming part of the normal organization of the Radiolarians in which they have been found; but even if they are so, and if we are compelled therefore to regard Radiolarians as multicellular, their multicellularity is of a radically different kind from that of any of the Metazoa, and none of their parts, whether truly cells or not, have any valid claim to the denomination of a tissue.

In regard to the relations of the Radiolaria to the other Protozoa, it is at present a disputed question whether it is the more natural arrangement to make on the one hand the Heliozoa, Radiolaria, and Thalamophora three distinct and coequal equivalent groups, or on the other hand to form two great groups, the one containing, as two subdivisions, the Heliozoa and Radiolaria, and the other the marine and freshwater Thalamophora. On the whole, notwithstanding undeniable similarities in external form, chemical composition, and otherwise, the author is inclined to keep the Radiolaria and Heliozoa provisionally apart as two equivalent and divergent groups, though unquestionably of all the above Protozoa the Heliozoa come nearest to the Radiolaria. The distinctions which seem to justify this are:

The author observes, however, that (5) is much weakened by the discovery of the salt-water Heliozoa; that with regard to (3), though the differences which exist between the reproductive processes are very great, yet greater differences exist between different Heliozoa, while the reproductive processes of so few Radiolarians have been examined that it would be rash to feel confident that no important divergences will be hereafter found amongst them in this respect, and that as to the capsule the distinction would be weakened if it should turn out that young Radiolarians, which have not yet acquired a capsule, nevertheless show a differentiation of their sarcode into an inner and an outer layer, like the medullary and cortical parts of Heliozoa, and the distinction would be broken down if it should be shown that certain adult Radiolarians have no capsule at all.

In dealing with the classification of the group the author suggests considerable modifications upon that of Haeckel. He objects (as unnatural) to Haeckel's division of the group into Monozoa or Monocyttaria and Polyzoa or Polycyttaria, the aggregation or non-aggregation of zooids into colonies being, in his opinion, a comparatively unimportant distinction, especially as individual zooids of the compound species are found also in a single and separate condition, and he suggests the union of Haeckel's fifteen groups into larger aggregations, reducing them to seven. These are:

VESICULATA.-Formed by separating from Haeckel's COLLIDA those forms (viz. Thalassicolla, Thalassolampe, Aulacantha, and Physematium) which have a nuclear vesicle-the presence or absence of which the author, following Hertwig, considers as of greater importance as a classificatory character than any characters derived from the skeleton— and uniting them with his AULOSPHÆRIDA and the other genera (Heliosphæra and Diplosphæra, part of his ETHMOSPHÆRIDA and the new form Myxobrachia), which possess that structure.

COLLOZOA.-Formed of the remaining COLLIDA (Thalassosphæra and Thalassoplancta) and Haeckel's SPHEROZOIDA and `COLLOSPHÆRIDA (which constitute his Polycyttaria).

POLYCYSTINA.-Formed of Haeckel's ACANTHODESMIDA and CYRTIDA, and the rest of his ETHMOSPHÆRIDA, associated together as being ectolithic, non-vesiculate, simple forms, the skeleton of which consists of more than detached spicula.

FLAGELLIFERA.-Formed of the genera Spongocyclia and Spongoastericus (part of Haeckel's SPONGURIDE) and Euchitonia, a genus of his DISCIDA-the possession of a large flagellum being, the author considers, a very important and natural character.

ACANTHOMETRIDA.-Formed by adding to the similarly named group of Haeckel those of his OMMATIDA (Dorataspis and Haliommatidum), whose radii meet together in the centre of the capsule-a very special and peculiar condition-and the author regarding as unnatural the separation from Haeckel's ACANTHOMETRIDA of these latter forms, which differ only in having tangential outgrowths from their radii so disposed as by their mutual junction to form an external shell. Haeckel's DIPLOCONIDA being also added as a third sub-section as presenting the special character of centrally-joined radii, regarding its conical structure as a mere special modification of radial structure.

ENTOSPHÆRIDA.-Comprising the remainder of Haeckel's OMMATIDA and part of his SPONGURIDA (Dictyoplegma, Spongodictyum, Rhizosphæra and Spongosphæra), the latter being an unnatural group, the possession of a spongy skeleton existing in very different forms. Adding also his CLADOCOCCIDA and CŒLODENDRIDA as forms possessing an intracapsular, more or less spheroidal shell-the latter from its exceedingly noteworthy mode of growth-by absorption and redeposition-possibly being entitled to be made a distinct primary group.

DISOIDA. Comprising the group so named by Haeckel (except Euchitonia) with the rest (Spongodiscida and Stylospongia) of his SPONGURIDA and his LITHELIDA.

The sections will then stand thus:

I. DISCIDA.-Mostly discoidal, sometimes elliptical, rarely cylindrical or spheroidal. Skeleton in part intracapsular, and consisting always of both circumferential and radial parts, which may be quite irregularly disposed, but which properly form an external, perforated shell, with an internal partition or spheroidal mass, forming a series of mutually communicating chambers, which are either concentrically or spirally arranged. No flagellum. Growth, multipolar or centrifugal. No nuclear vesicle.

II. FLAGELLIFERA.-With a flagellum. No nuclear vesicle. III. ENTOSPHÆRIDA. With an intracapsular spheroidal shell; not traversed by radii. No nuclear vesicle.

IV. ACANTHOMETRIDA.-With radial skeleton, the radii of which meet in the centre of the capsule, and consisting more or less of acanthin. No nuclear vesicle. Yellow cells generally absent.

V. POLYCYSTINA.-Simple, ectolithic forms, with more or less compact skeletons, often with unipolar growth. No nuclear vesicle.

VI. COLLOZOA.-Simple or compound. If single, then with the skeleton in the form of circumferential detached specula only. No nuclear vesicle.

VII. VESICULATA.-With a nuclear vesicle.

Oblique Light for Photo-micrography. In a letter written by Dr. Woodward to M. Deby, the Vice-President of the Belgian Microscopical Society, in September last, he describes the method he makes use of when it is necessary in photo-micrography to use very oblique light, as in the case of Nobert's test, Amphipleura pellucida, &c. A pencil of parallel solar rays (reflected by the heliostat and plane mirror) is intercepted by the cell containing the solution of ammonio-sulphate of copper and a diaphragm which only allows the passage of a circular pencil ofinch in diameter. The light enters parallel to the optic axis of the microscope placed horizontally and on the same level, but at a lateral distance (either right or left) of 3 inches. If the light is intercepted by a large achromatic prism of a focal length of about 3 inches, the desired obliquity can be obtained without difficulty. It is indispensable that the stage of the microscope should be very thin, or otherwise a false stage must be adopted like that supplied by Powell and Lealand. The best result is obtained when the rays are concentrated to a focus on the object itself. The illumination thus obtained is in general sufficient to produce negatives by the wet process up to 2500 diameters with three minutes' exposure.*

*

The Birth of a Rhizopod.-Professor Leidy has made some observations on this subject, which he records in the 'Proceedings of the Academy of Natural Sciences of Philadelphia':

I have long sought for the mode of multiplication of the testcovered Rhizopods, but thus far with little success. It appears as if the different forms with which we meet are always mature, and rarely are individuals seen with the ordinary characters which distinguish young from adult animals.

* Bulletin de. la Société Belge de Microscopie,' vol. iv. p. 61.