stantly colourless, specimens, apparently young, of Nebela bohemica, a coloured species, may be found colourless, as occurs in the Euglyphida and in Arcella. In the shell of Nebela bursella alone were perforations found, viz. two on each of the narrower sides; their function is, perhaps, to admit water into the spaces inside the shell, between the protoplasmic attachments of the body (called epipodia by Taránek), as they occur under similar conditions in Hyalosphenia, and the admission of water would have advantages for the animal. Taránek is unable to corroborate Leidy's statement that the smallest tests have the largest chitinous plates. In occasional examples of Nebela bohemica and collaris the plates are reduced to small granules, scattered over the surface, or they may be absent altogether, and the chitinous membrane left bare, or encrusted with foreign bodies. The plates consist of amorphous silica, as they resist combustion and weak acids and alkalies; strong sulphuric acid dissolves them slightly; they are firmly imbedded in the chitinous membrane, except in Quadrula. With regard to their origin, the author comes to the conclusion that they are formed by the animal itself, from their resemblance to those of the Euglyphidae, which are undoubtedly thus produced. The thickest plates are those of Lecquereusia, the thinnest those of Quadrula. The chitinous membrane is susceptible of staining, and thus, and from the mode in which foreign bodies are attached to it, evidently itself constitutes the only cementing substance employed; it sometimes projects outside the margins of the plates, and can here attach foreign bodies to itself. The sarcodic body of the Nebelida has the definiteness of form common to all the Monothalamia. As observed in specimens kept without food, the ectosarc is completely hyaline and structure- and colour-less; it is viscous, the outer part more so than the inner, which thus, and by acquisition of granules, gradually passes into the endosarc. The endosare has usually a pale yellow colour, and contains refractive bodies (microsomata) of two sizes. The nucleus is relatively large, and remains constantly at the back of the body, in the shell; a nucleolus is only occasionally noticed, has a dark or blueish colour, and a globular form; one or more nucleoli (up to five) may occur. A contractile vacuole was always observed, usually one or two; in Lecquereusia, Heleopera, and Quadrula three occur, closely associated. The author frequently finds in Nebelida chlorophyll masses derived from food, but never showing signs of being produced by the animal itself. The pseudopodia are formed by the streaming forward of the clear ectosarc, which divides into five to nine cylindrical lobes, the body at the same time becoming further removed from the inner wall of the test. The epipodia, when the animal is extended, form long filamentous processes of ectosarc. The animals live chiefly in peat-moss water, and prefer it when it is low; they either swim, with the mouth downwards, by movements of the extended pseudopodia (five to twelve in number), or creep by means of fewer pseudopodia, which attain the length of the shell, and have a flattened form; they drag the shell after them. Food is seized by and inclosed in a long pseudopodium, and is ultimately massed into small round nutriment-balls. Encystation takes place from June to September; the sarcode previously becomes almost opaque with nutritive substances, which later are resolved into strongly refractive oily globules of different sizes; the pseudopodia are withdrawn, the epipodia become shortened, the contractile vacuoles disappear, the nucleus becomes invisible, and the body withdraws more and more into the hinder part of the test, extruding various excreta such as diatom-shells, which are massed in the mouth of the test, forming the diaphragm, which becomes yellowish, probably from iron oxide. Taránek fully describes and figures with some classificatory and distributional tables the species obtained in Bohemia: viz. Nebela collaris; flabellulum; carinata; hippocrepis Leidy; bursella Vejdovsky; bohemica, a new species with compressed shell without processes, an oval entire pseudopodial opening, provided with a short neck; americana, a new species with a shell not compressed, flask-shaped, and devoid of spines; Heleopera petricola Leidy; Quadrula symmetrica F. E. Schulze; Lecquereusia spiralis Bütschli; and a new generic type called Corythion dubium, as yet only known by the test; this is small, has a pale yellow tint, is more or less broadly oval, and the pseudopodial opening is subterminal, roundish or oval to half-moon shaped, resembling that of Trinema acinus; it is made up of very small, oval, silicious plates (often round near the opening), arranged irregularly, and imbedded in the chitinous layer. BOTANY. A. GENERAL, including Embryology and Histology Living and Dead Protoplasm.-O. Loew returns to the subject of the different reactions of silver salts on living and dead protoplasm. By a fresh series of experiments he claims to have confirmed his previous results that the albumen of living cells alone has the power of reducing the silver, the death of the cell causing a chemical change in the albumen which deprives it of this power. Aldehydic Nature of Protoplasm.t-A. B. Griffiths, after reference to the work of Loew and Bokorny, Reinke, and others, as well as to a previous communication of his own,‡ describes his new experiments. He has examined the protoplasm of living and dead cells of Spirogyra, and finds that it reduces alkaline solutions of cupric salts; that crystals are found in it by treatment with weak sodium chloride, and that the addition of absolute alcohol to the cells of the Spirogyra Pflüger's Arch. f. d. Ges. Physiol., xxx. (1883) pp. 348-68. Cf. this Journal, i. (1881) p. 906; ii. (1882) pp. 67, 361, 440, 522; iii. (1883) p. 225. † Chem. News, xlviii. (1883) pp. 179–80. Journ. Chem. Soc.-Trans., xliv. (1883) p. 195. Ser. 2.-VOL. IV. causes the deposition of crystals of anhydrous dextrose. It is therefore probable that the reducing properties of protoplasm are due to this glucose, and that the crystals formed with sodium chloride are CH1208, NaCl + H2O. This view is supported by the following experiments :-Albumin (white of fresh egg) mixed with a small quantity of a very dilute solution of dextrose, when treated as above described, behaves in a manner precisely similar to the Spirogyra cells. Moreover, if the living plant is kept in the dark for a couple of days, and is then examined, none of these reactions are observed. This is evidently due to the dextrose being used up in the dark to nourish the cell-walls and tissues; for, after a short exposure to sunlight, the dextrose reappoars, and the usual phenomena are to be observed in the plant-cells. The author concludes with some remarks on the aldehydic nature of dextrose, on the assimilation of carbon by plants, and on the importance of researches on albumin. Embryo-sac and Endosperm of Daphne.-K. Prohaska brings forward the structure of the embryo-sac and mode of formation of the endosperm of Daphne as an illustration of the law that the polar nuclei do not always coalesce to form a secondary nucleus of the embryo-sac; and that the formation of the endosperm may take place without their assistance. The mature embryo of Daphne exhibits clearly two synergida and an ovum; while at its lower end is a group of more than three antipodal cells without any cell-wall. While the upper half of the embryo-sac contains but little protoplasm, its lower portion is filled with a dense mass, in which are two quite distinct nuclei with sharp outline, which can be shown to be the polar nuclei. In certain young states of the flower these nuclei are found in the two poles of the protoplasm, which is clearly detached from both the embryonic vesicles, and the antipodals; the lower nucleus subsequently approaches the upper pole; and still later, both are seen near to the embryonic vesicles forming a double nucleus. This double nucleus now moves gradually to the lower part of the protoplasm, which is no longer distinctly separable from the embryonic vesicles; protoplasm collects round it, and the number of antipodal cells increases after fertilization from 2 or 3 to 20. This double nucleus, therefore, corresponds to the secondary embryo-sac nucleus of other plants. It is therefore quite evident that a secondary embryo-sac nucleus is not formed after fertilization by the coalescence of the polar nuclei; but that, while this double nucleus remains, the formation of endosperm commences in the parietal layer of protoplasm by the free formation of nuclei. The following details are obtained from a number of preparations of Daphne Cneorum and Blagyana. The parietal protoplasm is often thickened in longitudinal threads, and contains moniliform strings of vacuoles both before and at the beginning of the formation of the endosperm. In it are seen small usually circular or elliptical portions of denser protoplasm filled with minute granules, shown by the *Bot. Ztg., xli. (1883) pp. 865-8 (1 pl.). application of pigments to be chromatin structures, and which develope into the nucleoli of the endosperm-nuclei. The nucleoli contain a very thin finely granular border of protoplasm; its granules, apparently grouped into short threads, surround the central nucleolus in a radial manner. The layer of protoplasm thus formed becomes gradually detached from the surrounding protoplasm of the embryosac, loses its radial framework, and forms at length a clear zone round the nucleolus containing only a few scattered granules. The nuclei in the parietal layer are sometimes formed separately, whether in the lower or upper part of the embryo-sac; sometimes in groups. Constitution of Albumin.*-From the reaction of superosmic acid O. Loew argues that the leucin and tyrosin compounds do not occur ready formed in the molecules of albumin; but that they are readily produced especially the benzol-nucleus of tyrosin-when albumin undergoes decomposition. The basis of the formation of albumin he considers to be a process of condensation rather than one of complicated synthesis. Fertilization of Sarracenia purpurea.†-F. Hildebrand describes the mode of pollination in Sarracenia purpurea, where the male and female organs are mature at the same time, but their relative position is such that fertilization is almost impossible without the assistance of insects, and self-fertilization is even then rendered very difficult. He also describes the arrangements for self-fertilization in a waterplant, Heteranthera reniformis, and for cross-fertilization in Salvia carducea, which differs from other species of the genus in the immotility of its stamens. Sexual Relations in Monoecious and Dicecious Plants.-F. Heyer has carried out a number of experiments with the view of determining the causes of the differentiation of sex in unisexual plants. As regards dioecious plants, the result of experiments with 21,000 specimens of Mercurialis annua and 6000 of Cannabis sativa was that external conditions have no influence on the production of seedlings of one or the other sex. The number of seedlings of each sex is very nearly the same; in the former species the proportion of male to female individuals was about as 105.85 to 100; in the latter, about as 86 to 100. Both species exhibit also secondary sexual differences in the vegetative organs. A second series of experiments to determine whether external conditions of temperature and soil caused any difference in the proportion of male and female flowers in monoecious plants (Urtica urens, Atriplex, Spinacia, Xanthium, Cucurbitaceae) yielded also only negative results. The general conclusion is that the sex of the individual is determined at an earlier period than the ripening of the seed; whether before or after fertilization cannot at present be said. * Pflüger's Arch. f. d. Ges. Physiol., xxx. ↑ Ber. Deutsch. Bot. Gesell., i. (1883) pp. Ber. Landwirthsch. Inst. Halle, Heft v. (1883) pp. 368–73. See Bot. Ztg., xli. (1883) p. 873. Corpuscula of Gymnosperms.-J. Gorosehankin has investigated the structure of these organs, chiefly in the Cycades, the species examined being Zamia pumila, Ceratozamia robusta, Lepidozamia Peroffskyana, Encephalartos villosus, and Cycas revoluta. The cellwall of the young corpusculum is always thin and quite homogeneous. In flowers (of Ceratozamia) about four months old, thin places have made their appearance in it in the form of roundish dots. When the ovules are mature (before fertilization) it is strongly thickened, and furnished with a number of conspicuous pits. The cell-wall is at all ages coloured blue by chloriodide of zinc, and is therefore composed of cellulose. Connected with each pit is a small canal, without any trace of the septum apparent; and the protoplasm of the corpuscula is distinguished by a number of protuberances equal in length to the canals. By treating the fresh endosperm with very dilute sulphuric acid, after the lapse of a day it becomes somewhat softened, and the corpuscles with their thick cell-walls can be easily removed; and, on addition of chloriodide of zinc, the pits in the latter can be very well made out. Tangential sections in alcoholic preparations of the corpuscula distinctly showed sieve-plates in the pits, by staining with chloriodide of zinc, or better with hematoxylin. The sieves were not all alike. In smaller pits they formed a uniform very thin network; in larger pits, besides the network, a coarser striation of the membrane was seen, which, however, passed gradually into the network. The sieve-plates are extremely thin, and require, to make them out, a very careful focusing of Hartnack's objective No. IX. Tinging with hæmatoxylin under very high powers shows that these plates are actually perforated. This can also be seen in longitudinal sections of fresh ovules treated with strong sulphuric acid, and then with iodine or eosin. The sulphuric acid causes a strong and rapid swelling of the cell-wall of the corpuscula, and a rupture of the threads of protoplasm that pass into the canals, the broken ends of which may be readily made out after treatment with iodine. These observations on the Cycadeæ prove, therefore, that the cellwall of the corpuscula consists of cellulose; and it appears to be thickened only on that side which faces the protoplasm of the corpuscle. It contains a large number of pits, furnished with true sieve-plates, through which the protoplasm of the cells of the adjacent layer of endosperm is in open communication with the protoplasm of the corpusculum. Similar sieve-plates were observed in the cell-wall of the corpuscles of a number of Coniferæ belonging to the Abietines and Taxineæ ; but in the Cupressineæ examined no trace of these pits could be detected. Comparative Structure of the Aërial and Subterraneous Stem of Dicotyledons.t-J. Constantin has made a comparative study of the stem above and below ground in a large number of dicotyledonous *Bot. Ztg., xli. (1883) pp. 825–31 (1 pl.). † Ann. Sci. Nat. (Bot.), xvi. (1883) pp. 5-176 (8 pls.). |