scholarly journals VIII. Observations on coprozoic flagellates: Together with a suggestion as to the significance of the kinetonucleus in the binucleata

1916 ◽  
Vol 207 (335-347) ◽  
pp. 375-412 ◽  
Keyword(s):  
Life History ◽  
Life Cycle ◽  
Alimentary Canal ◽  
The Other ◽  
Considerable Time ◽  
Parasitic Fauna ◽  
History Of ◽  
Active Condition ◽  
Soil Protozoa ◽  
The Subject

Since publishing, with Mr. Lapage, the first account of the life-cycle of Helkesimastix facicola , I have continued to work alone on the biology and life-history of the flagellates occurring in simple dung-cultures. In the course of this investigation, I have made certain observations which I wish here to record, together with one or two suggestions which I have to offer. The work promises to occupy considerable time before it is completed, and in the case of some of the forms studied I am not yet able to describe the life-cycle in its entirety. Little or no attention has been paid hitherto to the protozoa active in dung, and the study of this fauna is probably not without interest and importance in connection with the subject of the soil-protozoa. To distinguish those protozoa which are carried through the alimentary canal in a passive, encysted condition and become active and go through their life-history in the moist dung, Prof. Minchin has suggested, in the course of his lectures, the useful term coprozoic . The coprozoic fauna of goats and sheep is entirely different from their parasitic fauna, which has for its principal habitat the rumen. Neither the various specialised ciliates (of the fam. Ophryoscolecidæ ) nor the flagellates ( Sphæromonas , Trichomastix and Callimastix ), some of which are invariably present in the rumen, ever occur in an active condition in dung-cultures; and, on the other hand, I have never found any of the coprozoic flagellates active in the rumen-contents, when freshly examined. These facts, readily determined because the sets of forms in the two cases are entirely different, afford important confirmation of the view, now generally accepted, that the Entamæbæ —the truly parasitic forms—are quite distinct from the Amoebæ which develop in fæcal cultures, i. e .,coprozoic species.

scholarly journals The chromosome cycle in Coccidia and Gregarines

1915 ◽  
Vol 89 (610) ◽  
pp. 83-94 ◽  
Keyword(s):  
Life History ◽  
Life Cycle ◽  
Chromosome Numbers ◽  
Life Histories ◽  
The Other ◽  
Chromosome Cycle ◽  
History Of ◽  
Careful Investigation

Despite the large amount of work which has already been devoted to the study of the Coccidia and Gregarines, very little indeed is known definitely about the behaviour of the chromosomes in these Protozoa. Not only has the chromosome cycle been left uninvestigated and undescribed in the majority of these organisms which have hitherto been studied, but the very existence of chromosomes in the nuclear divisions at many stages in the life-history of certain forms has even been denied; and the most contradictory and unsatis­factory accounts have been given of that most important phase in the life-cycle of the chromosomes—the phase of meiosis, or reduction. In order to fill up this gap in our knowledge of the Sporozoa, we have made —during the last few years—a very detailed study of the chromosomes of a coccidian and a gregarine. One of us (C. D.) has investigated the coccidian Aggregate eberthi Labbé, whilst the other (A. P. J.) has studied the gregarine Diplocystis schneideri Kunstler. Careful investigation of these two organisms has shown that the nuclear divisions at all stages in the life-histories are mitotic, and that the chromosome numbers are remarkably constant.

The life history of Cyclops scutifer Sars (Copepoda: Cyclopoida) in a small lake of the Matamek River System, Quebec

1978 ◽  
Vol 56 (12) ◽  
pp. 2603-2607 ◽  
Author(s):  
J. J. Boers ◽  
J. C. H. Carter
Keyword(s):  
Life History ◽  
Life Cycle ◽  
Calanoid Copepod ◽  
River System ◽  
The Other ◽  
Cyclopoid Copepod ◽  
Small Lake ◽  
History Of ◽  
Cyclops Scutifer ◽  
Copepoda Cyclopoida

A study of the life history of the cyclopoid copepod Cyclops scutifer Sars in a small lake of the Matamek River System, Quebec, indicates a 1-year life cycle with four cohorts produced annually. The primary cohort overwinters as early nauplii and reaches maturity during midsummer when it spawns the primary cohort of the succeeding year. The other cohorts may merge with either each other or the primary cohort and contribute somewhat less to the overall cycle. Slower development of copepodites of the second cohort in 1976 may have been the result of an inadequate number of naupliar prey from the calanoid copepod Diaptomus minutus.

Life-history and ultrastructure of a new marine species of Proterospongia (Choanoflagellida)

1983 ◽  
Vol 63 (1) ◽  
pp. 135-160 ◽  
Author(s):  
Barry S. C. Leadbeater
Keyword(s):  
Electron Microscopy ◽  
Life History ◽  
Life Cycle ◽  
Single Cells ◽  
Marine Species ◽  
The Other ◽  
Developmental Problems ◽  
Starting Point ◽  
History Of ◽  
Whole Mounts

The morphology and microanatomy of two different phases in the life history of a single new marine choanoflagellate (Proterospongia choanojuncta sp.nov.) have been documented and described with the aid of light microscopy and from electron microscopy of whole mounts and sections of material in clonal culture. Completion of the life-cycle has been repeatedly achieved in cultures established from single cells, regardless of which phase is used as a starting point. One phase is colonial and motile (the Proterospongia phase) and the other unicellular and sedentary (the Choanoeca phase). Taxonomic, nomenclatural and developmental problems are summarized and discussed.

scholarly journals The life-cycle of the nodule organism, bacillus radicicola ( Beij. ), in soil and its relation to the infection of the host plant

1926 ◽  
Vol 99 (699) ◽  
pp. 427-451 ◽  
Keyword(s):  
Life History ◽  
Life Cycle ◽  
Host Plant ◽  
Internal Structure ◽  
Mother Cell ◽  
Leguminous Plant ◽  
Young Culture ◽  
History Of ◽  
The Subject ◽  
Straight Rod

The existence of changes in the form of Bacillus radicicola has been known since Beijerinck (2) first isolated it in 1888 from leguminous plant nodules. He observed the motile “swarmer” stage as well as the branching forms, whose nature was already the subject of controversy. About the same time the development of straight-rod forms of the organism was described by Prazmowski (14). Numerous writers have since observed the existence of the organism in the three conditions of straight rods, branching rods and cocci (for references, see Löhnis, 1921 (10)). In 1916 Löhnis and Smith (11) claimed that the various forms constituted a definite life-cycle through which the organism normally passes, and this cycle, as seen in cultures, was carefully described in 1919 by Bewley and Hutchinson (3). In a vigorous young culture, the predominating form of the organism is a short, evenly staining rod (fig. 1). These rods soon undergo a change in internal structure, the staining material becoming segregated into bands crossing the cell. During this banded stage the cells frequently become swollen, distorted, and branched, the so-called “bacteroids” (Brunchorst (4)), but this irregularity of form is not an essential part of the life-cycle, but would appear to be a response to conditions of the environment (Buchanan, 1909) (5). The banded cells give rise to the cocci by further condensation of the bands. The origin of the cocci within the mother-cell was described and illustrated in 1891 by Morck (12), who was the first to appreciate the relation of the internal structure of the cell to the life-history of the organism. The cocci are usually released in a non-motile condition, and afterwards develop flagella, becoming actively motile, the “swarmers” of Beijerinck (2). Under certain conditions, however, the cocci develop flagella while still enclosed within the mother-cell. This condition has been described by Greig-Smith (8) and the observation confirmed by one of the present authors (7). The cocci eventually become elongated and thus pass into the unbanded rod stage. The flagella, which are developed on the cocci, persist after this elongation, but are soon lost: the rods then become non-motile. The development of motility in a culture is thus intimately associated with the appearance of the coccus stage.

scholarly journals I. The Croonian Lecture.—On the theory of the vertebrate skull

1859 ◽  
Vol 9 ◽  
pp. 381-457 ◽  
Keyword(s):  
Natural History ◽  
Biological Science ◽  
The Other ◽  
Small Space ◽  
Half Century ◽  
Organic Structure ◽  
History Of ◽  
The Subject ◽  
Articles Of Faith ◽  
The Mind

The necessity of discussing so great a subject as the Theory of the Vertebrate Skull in the small space of time allotted by custom to a lecture, has its advantages as well as its drawbacks. As, on the present occasion, I shall suffer greatly from the disadvantages of the limitation, I will, with your permission, avail myself to the uttermost of its benefits. It will be necessary for me to assume much that I would rather demonstrate, to suppose known much that I would rather set forth and explain at length; but on the other hand, I may consider myself excused from entering largely either into the history of the subject, or into lengthy and controversial criticisms upon the views which are, or have been, held by others. The biological science of the last half-century is honourably distinguished from that of preceding epochs, by the constantly increasing prominence of the idea, that a community of plan is discernible amidst the manifold diversities of organic structure. That there is nothing really aberrant in nature; that the most widely different organisms are connected by a hidden bond; that an apparently new and isolated structure will prove, when its characters are thoroughly sifted, to be only a modification of something which existed before,—are propositions which are gradually assuming the position of articles of faith in the mind of the investigators of animated nature, and are directly, or by implication, admitted among the axioms of natural history.

Albert Schweitzer and the Jews

2014 ◽  
Vol 107 (3) ◽  
pp. 363-398
Author(s):  
James Carleton Paget
Keyword(s):  
Jewish Community ◽  
Academic Career ◽  
Significant Degree ◽  
The Other ◽  
Personal Contact ◽  
Christian Communities ◽  
History Of ◽  
The Subject ◽  
Long Life ◽  
The One

Albert Schweitzer's engagement with Judaism, and with the Jewish community more generally, has never been the subject of substantive discussion. On the one hand this is not surprising—Schweitzer wrote little about Judaism or the Jews during his long life, or at least very little that was devoted principally to those subjects. On the other hand, the lack of a study might be thought odd—Schweitzer's work as a New Testament scholar in particular is taken up to a significant degree with presenting a picture of Jesus, of the earliest Christian communities, and of Paul, and his scholarship emphasizes the need to see these topics against the background of a specific set of Jewish assumptions. It is also noteworthy because Schweitzer married a baptized Jew, whose father's academic career had been disadvantaged because he was a Jew. Moreover, Schweitzer lived at a catastrophic time in the history of the Jews, a time that directly affected his wife's family and others known to him. The extent to which this personal contact with Jews and with Judaism influenced Schweitzer either in his writings on Judaism or in his life will in part be the subject of this article.

scholarly journals On the Tumulus of Choban Tepeh in the Troad

1897 ◽  
Vol 17 ◽  
pp. 319-320 ◽  
Author(s):  
Frank Calvert
Keyword(s):  
The Other ◽  
The Road ◽  
Ancient City ◽  
History Of ◽  
The Subject ◽  
On The Road ◽  
The Hill

I derive the materials of the present paper from some memoranda which I find amongst my archaeological notes and which relate to certain explorations to which I was not a party, made so long ago as 1887. I have thought that the particulars then obtained may be deemed sufficiently interesting to deserve a record in the history of Trojan archaeological discovery.The subject is one of the four small tumuli dotted about and near the hill of Balli-Dagh, the crest of which according to the now exploded theory of Le Chevalier (1785) was supposed to represent the Pergamos of Troy. In a memoir contributed to the Journal of the Archaeological Institute of 1864, I proved that the site in question was no other than that of the ancient city of Gergis. In the same paper I gave an account of the results of the excavation of one of the group of three tumuli on Balli-Dagh, the so-named Tomb of Priam. The other two, namely Le Chevalier's Tomb of Hector, and an unnamed hillock, were excavated respectively by Sir John Lubbock (about 1878) and Dr. Schliemann (1882) without result. The present relates to the fourth mound on the road between the villages of Bournarbashi and Arablar (as shown in the published maps), which goes by the name of Choban Tepeh (Shepherd's hillock) and the Tomb of Paris, according to Rancklin (1799).

XXIII. On the water-barometer erected in the hall of the Royal Society

1832 ◽  
Vol 122 ◽  
pp. 539-574 ◽  
Keyword(s):  
Royal Society ◽  
Physical Science ◽  
The Other ◽  
Metallic Tube ◽  
French Academy ◽  
History Of ◽  
The Subject ◽  
The Common ◽  
Academy Of Sciences ◽  
Made In

I have for some time entertained an opinion, in common with some others who have turned their attention tot he subject, that a good series of observations with a Water-Barometer, accurately constructed, might throw some light upon several important points of physical science: amongst others, upon the tides of the atmosphere; the horary oscillations of the counterpoising column; the ascending and descending rate of its greater oscillations; and the tension of vapour at different atmospheric temperatures. I have sought in vain in various scientific works, and in the Transactions of Philosophical Societies, for the record of any such observations, or for a description of an instrument calculated to afford the required information with anything approaching to precision. In the first volume of the History of the French Academy of Sciences, a cursory reference is made, in the following words, to some experiments of M. Mariotte upon the subject, of which no particulars appear to have been preserved. “Le même M. Mariotte fit aussi à l’observatoire des experiences sur le baromètre ordinaire à mercure comparé au baromètre à eau. Dans l’un le mercure s’eléva à 28 polices, et dans Fautre l’eau fut a 31 pieds Cequi donne le rapport du mercure à l’eau de 13½ à 1.” Histoire de I'Acadérmie, tom. i. p. 234. It also appears that Otto Guricke constructed a philosophical toy for the amusement of himself and friends, upon the principle of the water-barometer; but the column of water probably in this, as in all the other instances which I have met with, was raised by the imperfect rarefaction of the air in the tube above it, or by filling with water a metallic tube, of sufficient length, cemented to a glass one at its upper extremity, and fitted with a stop-cock at each end; so that when full the upper one might be closed and the lower opened, when the water would fall till it afforded an equipoise to the pressure of the atmo­sphere. The imperfections of such an instrument, it is quite clear, would render it totally unfit for the delicate investigations required in the present state of science; as, to render the observations of any value, it is absolutely necessary that the water should be thoroughly purged of air, by boiling, and its insinuation or reabsorption effectually guarded against. I was convinced that the only chance of securing these two necessary ends, was to form the whole length of tube of one piece of glass, and to boil the water in it, as is done with mercury in the common barometer. The practical difficulties which opposed themselves to such a construction long appeared to me insurmount­able; but I at length contrived a plan for the purpose, which, having been honoured with the approval of the late Meteorological Committee of this Society, was ordered to be carried into execution by the President and Council.

scholarly journals On Apogamy and the development of Sporangia upon fern prothalli

1898 ◽  
Vol 63 (389-400) ◽  
pp. 56-61
Keyword(s):  
Life History ◽  
Point Of View ◽  
The Other ◽  
Normal Life ◽  
Other Hand ◽  
General Importance ◽  
Two Generations ◽  
History Of ◽  
Alternation Of Generations

The two most important deviations from the normal life-history of ferns, apogamy and apospory, are of interest in themselves, but acquire a more general importance from the possibility that their study may throw light on the nature of alternation of generations in archegoniate plants. They have been considered from this point of view Pringsheim, and by those who, following him, regard the two generations as homologous with one another in the sense that the sporophyte arose by the gradual modification of individuals originally resemblin the sexual plant. Celakovsky and Bower, on the other hand, maintaint the view tha t the sporophyte, as an interpolated stage in the life-history arising by elaboration of the zygote, a few thallophytes.

scholarly journals Effect of NaCl on seed germination in some Centaurium Hill. Species (Gentianaceae)

2007 ◽  
Vol 59 (3) ◽  
pp. 227-231 ◽  
Author(s):  
S. Zivkovic ◽  
M. Devic ◽  
B. Filipovic ◽  
Z. Giba ◽  
D. Grubisic
Keyword(s):  
Life History ◽  
Salt Tolerance ◽  
Seed Germination ◽  
Gibberellic Acid ◽  
White Light ◽  
The Other ◽  
Distilled Water ◽  
Nacl Concentration ◽  
History Of ◽  
Species Specific

The influence of high NaCl concentrations on seed germination in both light and darkness was examined in the species Centaurium pulchellum, C. erythraea, C. littorale, C. spicatum, and C. tenuiflorum. Salt tolerance was found to depend on the life history of the seeds. To be specific, seeds of all five species failed to complete germination when exposed to continuous white light if kept all the time in the presence of 100-200 mM and greater NaCl concentrations. However, when after two weeks NaCl was rinsed from the seeds and the seeds were left in distilled water under white light for an additional two weeks, all species completed germination to a certain extent. The percent of germination not only depended on NaCl concentration in the prior medium, but was also species specific. Thus, seeds of C. pulchellum, C. erythraea, and C. littorale completed germination well almost irrespective of the salt concentration previously experienced. On the other hand, seeds of C. tenuiflorum completed germination poorly if NaCl concentrations in the prior media were greater than 200 mM. When seeds after washing were transferred to darkness for an additional 14 days, they failed to complete germination if previously imbibed on media containing NaCl concentrations greater than 400 mM. However, the seeds of all species, even if previously imbibed at 800 mM NaCl, could be induced to complete germination in darkness by 1 mM gibberellic acid. .

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