He is inclined, therefore, to think that the microbe of rabies is infinitely small, a mere dot in shape, and not like a bacillus or a dumbbell-shaped micrococcus. The only method known at present by which these granulations may be isolated from the other and nervous elements is the following: -Virus taken from the brain of an animal that has died of rabies is injected into the veins of a rabid animal at the moment when asphyxia commences. In a short time the normal nervous elements disappear from the blood in which only the just-mentioned minute granulations are now to be found. These may be stained by anilin dyes, but as the author is careful to point out, it is not yet definitely proved that these granulations are the microbes of rabies. It has been found that while the trepanation-experiments are succeeded by desire to bite and "rabid barking "-furious rabiesinjection experiments produce only paralytic rabies. If, however, exceedingly minute quantities of virus are injected, furious rabies ensues. On the other hand these minute quantities extend the period of incubation, and if the poison is diluted beyond a certain extent the inoculation has no effect. But these minute and inoffensive doses do not give protection against the effect of larger doses. In rare cases the effects of the poison disappear to reappear with mortal result after some days. Entirely negative results have been obtained in reference to the pretended diminution of the poison by the influence of cold and by its passage from the mother to the foetus. Especial attention has been given to the very important question of the alteration of the character of the virus, and it has been found that the passage of the rabic virus through several species does more or less profoundly modify its virulence. Pasteur and his assistants now possess a virus which gives rabies to the rabbit in seven or eight days, and that with remarkable constancy; another virus has a similar effect on guinea-pigs. Pasteur has already made known the curious fact that he has in his laboratory some dogs that are refractory to the virus of rabies, but he has not till now been able to say whether that was due to their natural constitution or not. He now finds that it is not so, but that he can by a system of inoculations of different kinds, make any number of dogs refractory; indeed he has now twenty-three. For the present he confines himself to this statement, but it is clearly one of great importance, as man only becomes rabid directly or indirectly from the bite of a dog. He concludes: "Could not human medicine profit by the long duration of the period of incubation to try and estab lish in this interval of time, before the appearance of the first symptoms of rabies, the refractory condition of subjects that have been bitten? Much, however, remains to be done before this hope can be realized." Yeast-ferments.*-Continuing his researches on the ferment of beer, E. C. Hansen observes that there are in nature a large number *Allg. Zeitschr. f. Bierbrauerei u. Malzfabrikat, 1883, p. 871. See Bot. Centralbl., xvii. (1884) p. 169. Cf. this Journal, iii. (1883) p. 252. of fungi belonging to the most distinct groups which are capable of developing saccharomyces-like cells, by budding in nutrient solutions; but differing from that genus in not forming endogenous spores. Some of these fungi induce alcoholic fermentation, behaving in this respect like Saccharomyces cerevisia. The author has made a careful examination of one of these unknown species. It propagates itself in beer-wort by budding, causing the higher fermentation, and showing in this respect a close relationship to Saccharomyces ellipsoideus. But under conditions where S. cerevisiae would produce 6 vol. per cent. of alcohol, it produces scarcely 1.5 per cent. It also exhibits a great difference in its fermentive action, the chemical soluble ferment or invertin being entirely wanting, although it ferments saccharose as such. This establishes the fact frequently controverted, that saccharose can be directly fermented without previous immersion. The fungus readily produces a perfect mycelium. Although its cells, when cultivated in beer-wort, altogether resemble typical S. ellipsoideus or cerevisia, they do not produce endogenous spores. Action of Cold on Microbes.*-R. Pictet and E. Yung find that various organisms, such as bacilli, when subjected to a temperature of 70° C. for 108 hours, and to 130° for 20 hours, are not destroyed; others, such as Torula and the vaccine microbe, lost their power of producing fermentation. Algæ. Fertilization of Cutleria.t-E. de Janczewski has paid special attention to the development and mode of fertilization of Cutleria adspersa, growing at Antibes. This species is strictly dioecious; but the male and female plants are often so intimately united at their base that it is practically impossible to separate them. They can only be distinguished by the different colours of their sori, orange in the male, very dark brown in the female plants. Each mature sporangium consists usually of 16 or sometimes of 32 cells, from each of which escapes a motile oosphere. This usually takes place early in the morning. The normal number of antherozoids produced in an antheridium is 128. The emission of antherozoids occurs at the same time as that of the oospheres; their period of motility does not exceed 12 hours at the outside. Their form and structure are precisely that of the Fucaces. Each of them has two vibratile cilia, and a bright orange granule. The motile oospheres bear a close resemblance to the zoospores of the Phæosporeæ, except that they are considerably larger. The whole of the oosphere is of a brown colour, except the anterior portion which constitutes a colourless beak. This beak bears at one side a slight swelling, to which are attached two vibratile cilia. The colourless protoplasm of the oosphere contains a number of brown chromoplastids, and of much smaller, colourless, * Comptes Rendus, xcviii. (1884) pp. 747-9. † Ann. Sci. Nat. (Bot.), xvi. (1883) pp. 210-26 (2 pls.). highly refractive globules; there is no nucleus. Near the point of insertion of the vibratile cilia is a single large orange granule. The motility of the oospheres lasts as long as that of the antherozoids, and is equally affected by light. As long as the oospheres are in motion, the antherozoids display no affinity for them; but as soon as the oospheres have lost their cilia and come to rest, the antherozoids are attracted to them. They move rapidly round them, finally come in contact with them, lose their cilia, and become absorbed into their substance. A single antherozoid is sufficient to impregnate an oosphere. The fertilized oosphere contains the two orange granules derived from the male and female elements. It immediately becomes invested with a cell-wall, and begins to germinate the next day, dividing first of all into two cells, one of which is much larger than the other. Zoospores which germinate without fecundation, resembling those of Zanardinia, are also probably present. They are found in unilocular zoosporangia, and resemble the motile oospheres except in their much smaller size. Cutleria exhibits in its structure several important variations from the Fucacem. The antheridia are pluricellular in the former, unicellular in the latter. The oospheres of the Fucaces are immotile, and do not contain any orange granules; except in the latter point they resemble the oospheres of Cutleria after they have come to rest. The nearest affinity of the Cutleriacea appears to be with the Ectocarpaces. Ectocarpus Lebelii and secundus possess antheridia which produce antherozoids precisely resembling those of the Cutleriaceae and of the Fucaces, and equally incapable of independent germination. They also have plurilocular sporangia exactly like those of Cutleriaces. The plurilocular sporangia of other species of Ectocarpus and of the Phæospore generally must be regarded as female organs, and the bodies which emerge from them not as true zoospores, but as motile oospheres homologous to those of Cutleriaceae, which, in default of male organs, germinate without fecundation, offering an example of constant parthenogenesis. The same is also probably the case in the pelagic Cutleria multifida. The unisporous sporangia of Tilopteris, Haplospora, and Scaphospora are evidently homologous with the plurilocular sporangia of Ectocarpus; their oospheres appear, under certain conditions, to germinate parthenogenetically. The occurrence of parthenogenesis normally in the greater number of Phæospores, and exceptionally only in the Cutleriaceae, must be regarded as placing this family at the head of the group. Endoclonium polymorphum.*-Under this name a new parasitic alga is described by M. Franke. It has been observed only on Lemna gibba, on which it occurs in two forms, one endophytic in the air-cavities beneath the stomata on the upper side of the frond; the other epiphytic, on all parts of the host. The two forms are connected by an imperfect alternation of generations; but the same *Cohn's Beitr. Biol. Pflanzen, iii. (1883) pp. 365–76 (1 pl.). Ser. 2.-VOL. IV. 2 G form may also repeat itself through a number of generations. The zoospores of the endophytic protococcus-like form germinate after coming to rest, on the surface of the Lemna, and give rise to the stigeoclonium-like epiphytic form. This produces macrozoospores, with four cilia, which continue to repeat the same form, and microzoospores, which sometimes, without conjugation, either enter the air-cavities beneath the stomata, and develope the endophytic form, or repeat the epiphytic form on the surface of the host: at other times they conjugate, and the zygozoospore also probably enters the aircavities and gives rise to the endophytic form. When cultivated in a moist atmosphere the cells of the epiphytic form increase in size and multiply rapidly, and, like the microzoospores and macrozoospores, may pass into a resting condition, their cell-wall thickening, but without any formation of jelly. The apical cells of the filaments finally put out long apical points destitute of chlorophyll. Both kinds of zoospore have a red eye-spot, and are formed by repeated bipartition, with the exception of the macrospores, which are produced singly in the sporangia. The macrospores are 13.5 μ long and 10 μ broad, and provided with four cilia; the microspores are biciliated, and 7.5 μ long by 3.5 broad. The endophytic form produces zoospores of one kind only, resembling the microzoospores. The parasite occurs especially on the white dead parts of the Lemna, where it produces dark green spots visible to the naked eye. Godlewskia, a new Genus of Cryptophyceae.*-E. de Janczewski has found, growing on Batrachospermum in a ditch near the botanic garden of Cracow, a new species and genus of algae, to which he gives the name Godlewskia aggregata. It is distinguished at a glance from its host by its beautiful blue-green colour. Each individual consists of a basal flask-shaped cell or sterigma, and a number of smaller globular cells, borne in a row at its apex, conidia, formed by continued division of the sterigma. These conidia germinate directly, but do not separate easily from the parent sterigma, sometimes as many as two generations being found still attached to it, each basal conidium developing into a sterigma. Godlewskia must be assigned to the family Chamaesiphoneæ among Cryptophyceae. Sexuality in Zygnemaceæ.t-A. W. Bennett has investigated the reproduction of the Zygnemacea, with a view to the solution of the question: Is it of a sexual character? De Bary, twenty-five years ago, and since then, Wittrock, have instanced what they have thought to be sexual differences between the conjugating cells, though most later writers rather ignore any essential physiological distinction. Mr. Bennett has directed his investigations chiefly to the genera Spirogyra and Zygnema, and from these he supports the inference of the above-mentioned authors. He finds there is an appreciable * Ann. Sci. Nat. (Bot.), xvi. (1883) pp. 227-30 (1 pl.). difference of length and diameter in the conjugating cells, that deemed the female being the larger. The protoplasmic contents pass only in one direction, and the change first commences in the chlorophyll-bands of the supposed male cells, with accompanying contraction of the protoplasmic contents. The genera Mesocarpus, Staurospermum, and the doubtful form Craterospermum, on the whole substantiate the view above enunciated of sexuality. Movements of the Oscillarieæ.-In addition to the oscillatory movements of the Oscillaries, creeping and rotating movements of the protoplasm are also to be perceived, especially in those species where the cell-wall is thin and flexible, as Oscillaria tenerrima and ærugineocærulea. These have been more closely investigated by A. Hansgirg. The oscillating motion commences as soon as the filament has become fixed to a substratum by means of the mucilaginous substance excreted on the surface of the cell-wall. This extremely thin layer of mucilage often forms a hollow tube behind the creeping filament. It is not coloured brown by iodine like protoplasm, and takes only a passive, not an active part in the movement of the filament. The motive power which causes the gliding motion of the filament on a solid substratum resides in the protoplasmic contents of the cells, and is connected with osmotic currents. In the protoplasm which had escaped from the broken end of a filament of O. princeps, the author observed a number of amoeboid cells, from 9 to 12 in diameter, nearly spherical in form, and putting out colourless pseudopodia about twice the length of the central body, and to these he attributes the motile power of the protoplasm of the filament. The so-called "cilia" which proceed from the terminal cells of the filament of O. aerugineo-cærulea, do not participate in its motion except passively, and are, according to the author, independent parasitic organisms of the nature of Leptothrix. In all the cells of the filaments of Oscillaria, the turgidity is unusually great, and the dividing septa experience great differences of pressure from variations in the tension. The cause of the oscillating motion appears to be that the protoplasm takes up water more rapidly, and consequently swells to a greater extent, than the enveloping sheath of mucilage. Several species can retain their vitality to an extraordinary extent, and for a long time after losing their water and becoming completely dried up. A series of experiments made with a variety of substances led the author to the conclusion that the movements of the Oscillariem are caused mainly by the osmotic forces and forces of imbibition, which act on the protoplasmic contents of the cells, and not to any external layer of protoplasm. In those species where the filaments are inclosed in an osmotic mucilaginous sheath, in which they move alternately backwards and forwards, this takes place chiefly by osmotic processes in the protoplasmic contents of the cells, in consequence of which the turgidity becomes greater alternately in the *But. Ztg., xli. (1883) pp. 831-43 (1 pl.). |