摘要:

Summary1. A survey of accounts of the histology of the blood system in the various families of the Oligochaeta and Polychaeta has revealed a surprising lack of agreement among descriptions not only of the same family, but often of the same genus or species. There are several reasons for this. Many annelid vessels are very small and are difficult objects for histological investigation. They have rarely been examined in detail whilst alive. Few people have employed special staining methods for distinguishing connective tissue fibres from muscle fibres; nearly always both are present, and they have often been confused with each other. The lack of any comprehensive and analytic review of the scattered literature on the subject seems to be one of the reasons for many of the discrepancies.2. Not only is there disagreement in factual descriptions of histological structure, but, since 1904, there has also been much discussion about the interpretation of observations, occasioned by two important rival theories of the origin of the annelid blood system (Lang, 1904; Vejdovsky, 1905).3. Lang postulated that the haemocoel occupies the site of the blastocoel. The gut sinus is bounded internally by the basement membrane of the gut epithelium. The outer wall of the sinus and the walls of the vessels are derived from splanchnopleuric mesoderm, and consist of the peritoneum and its basement membrane (Leydig's ‘Intima’). An endothelium, where present, is a secondary component of the walls; its origin is obscure.4. Vejdovsky considered that the gut sinus is intra‐endodermal. The blood bathes the gut epithelium, the basement membrane of which is situated in the outer wall of the sinus. This outer wall, and the walls of the blood vessels, have both endodermal and mesodermal components. The latter is the peritoneum. The endodermal component consists of a skeletal coat (vasothelial membrane, equivalent to Leydig's intima) and vasothelial cells of endodermal origin. These cells, corresponding to the endothelium of other authors, are primary components of the walls.5. It has been shown that Vejdovsky's observations disagree with those of previous workers, and that later research has not confirmed them. They are open to criticism because he used inadequate staining methods.6. The theories of Lang and Vejdovsky led to controversy in the interpretation of observations. They also stimulated a large amount of research, much of which was uncritical. For example, two adherents of Vejdovsky's theory noticed a basement membrane on the gut epithelium, but reiterated the statement that the sinus is intra‐endodermal. Similarly, many supporters of Lang's theory paid little attention to cells lying on the inner surface of the skeletal coat, because Lang considered that they are secondary components of the wall; they have frequently been dismissed as sessile blood corpuscles.7. An analysis of all the literature on the histology of the blood system in the Oligochaeta and Polychaeta has led to the following conclusions, which should be regarded as tentative until more careful and detailed observations have been made.8. The walls of the blood system contain a homogeneous connective tissue membrane. This skeletal coat is covered by a peritoneum which is differentiated in various ways in different vessels. On the inner surface of the skeletal coat lies a discontinuous endothelium.9. The endothelium probably often takes the form of branched cells joined together by their processes. Endothelial cells are flat, and their flat oval nuclei are elongated in the direction of the length of the vessel. Fibrils have sometimes been found in the cells, but have never been shown to be contractile. However, there is evidence that the endothelium may in some cases be contractile. Iron and chloragosome‐like bodies have occasionally been found in it.10. The skeletal coat is a continuous homogeneous membrane of a collagenous substance. It is linked by fibres with connective tissue outside the vessel. It becomes longitudinally folded when the vessel contracts.11. The peritoneum is differentiated in various ways, probably correlated with the size and contractility of the vessels. It may be a simple flat epithelium without fibrils; an epithelium with intracellular muscle fibrils; a muscle‐epithelium; a coat of muscles with a cellular covering consisting both of peritoneal epithelial cells and of the cell bodies of the muscle fibres; a coat of muscles covered by a complete peritoneal epithelium.12. The muscle fibres are of the nematode type, i.e. they consist of a cell body containing the nucleus, and processes containing the muscle fibrils. The nucleus is large and nearly spherical and has a conspicuous nucleolus. On small vessels the muscle cells are sometimes stellate, resembling the Rouget cells of vertebrate capillaries. Like Rouget cells, they can be vitally stained with methylene blue.13. Various descriptions of the internal structure of the larger muscle fibres have been given. Some are apparently unstriped. Others have a double oblique striation. Others are said to show a true cross‐striation. In some cases the fibre apparently contains both striped and unstriped fibrils.14. Several theories of the origin of the various coats in annelid vessel walls have been advanced (notably by Lang and Vejdovsky). Evidence based on comparative anatomy, embryology and studies on regeneration suggests that Lang's theory is to be preferred. The haemocoel occupies the site of the blastocoel. The walls of the blood system are entirely mesodermal. The walls of the larger vessels, and the outer wall of the gut sinus are formed by the splanchnopleuric mesoderm, to which belong the peritoneum and the skeletal coat. Nothing is known about the origin of the endothelium.I wish to acknowledge the help I have gained by many discussions of this subject with Dr A. Stock. I am grateful to him and to Dr B. M. Walshe for reading and criticizing t

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1949.tb00573.x

出版商:Blackwell Publishing Ltd    

年代:1949

数据来源: WILEY

摘要:

Summary1. The reproductive cycle of tsetse flies occupies a minimum of 55 or 56 days at 23o, made up of 12 days' ovarian development of the first egg (always in the right ovary), 3 or 4 days' embryonic development, 7 days' larval growthin utero, and 33 days as a pupa underground; the male pupal period is longer by about 6%. Second and later larvae follow the first at 11‐day intervals, equal numbers of each sex. A special uterine organ assists eclosion and ecdysis.2. The cycle varies with temperature but not with humidity. Failure to inseminate causes irregularities in ovulation; in nature the females almost invariably copulate once only, when seeking or taking the first meal. Males are potent after they are 4–6 days old. Some species will cross with each other but the male hybrids are infertile.3. During the rains pupae are widely scattered, which has led observers to suppose that breeding is then interrupted; breeding grounds may also shift with season.4. Pupae can survive slight frost; lethal high temperature varies from 40 to 57oaccording to shortness of exposure. They can develop within a range from about 16–31o, but at the extremes non‐viable flies result, and continual exposure to 30osterilizes the ovaries of at least one species.5. Loss of weight during pupal life is nearly independent of initial weight; it depends on humidity but not on temperature.6. The size and weight of pupae depends on the temperature at which the mothers were living, and also on the timing of meals; three large meals are needed to produce a large larva, one shortly after larviposition and the third about 3 days before the larva is born.7. Natural mortality of pupae (excluding predation and parasitization) may be zero in certain sites, but normally varies from 8 to 30 or 50% with temperature.8. Before the first meal the ptilinum remains eversible, the chitin is soft and the fly is called teneral. The constitution of the pupa, and of the teneral fly of given age, varies with the species, but the water and fat proportions are fairly constant, and there is little difference between the sexes. Smaller pupae and flies have proportionally less fat. Mean weight may vary seasonally in the proportion of 4–5.9. Loss of water by starving teneral flies (and of course survival) is governed by temperature and humidity; loss of fat is governed by temperature; but the effect of humidity is controversial. Smaller individuals lose proportionally more weight than larger ones, and are less viable in the‐field. Death at low humidities is caused by water loss, before the fat reserves are used up.10. About 2 mg. of fat is probably synthesized at each meal in nature, but in captivity fat synthesis is poor. Fat is also accumulated over several meals, at least up to the age of 3 weeks. It is doubtful whether water loss is or could be compensated by metabolism of fat.11. Lethal high temperatures depend on humidity and time of exposure of the flies, as well as on species, but temperatures of 38–40ofor 1–3 hr. may be lethal, especially at high humidity. As with pupae, light frost is tolerated for short periods, at least by some species.12. The salivary glands secrete an anticoagulin and the mesenteron a strong coagulin; species feeding much on reptilian or avian bloods, which tend to clot easily, have larger salivary glands. The digestive enzymes are mainly proteolytic. The chitinous peritrophic membrane is formed afresh from the proventriculus at each meal, keeping pace with the enclosed blood on its progress along the mesenteron.13. Precipitin tests have indicated that large bovids, giraffe and wart‐hog are important hosts ofGlossina swynnertoni, but that zebra are not. Corpuscle measurements suggest that during the rainsG. morsitans submorsitansfeeds mainly on small antelope and wart‐hog;G. longipalpiscan apparently survive on small antelope alone. Destruction or reduction of large ungulates sometimes eliminatesG. morsitans;exceptionally this species maintains itself on man and his domestic animals. Five per cent ofG. morsitanscommonly take avian blood, butG. swynnertoni, G. longipalpisandG. pallidipeshave an almost exclusively mammalian diet.14. On the other hand,G. palpalisandG. tachinoidestake much nucleated blood, and are scarcely affected by the absence of ungulates.15. The eyes ofGlossinaare not more accurate than those of other Diptera, but may be adapted to perceive movement.G. swynnertonican see large animals in a good light between 150 and 200 yards away and can scent them between 60 and 100 yards up‐wind; butG. morsitanswith antennae occluded came to man as readily as normal flies.16. Flies of themorsitansgroup feed about every 4th day at 23o, but the hunger cycle depends on temperature and probably humidity; more weight is lost shortly after the meal than later on.17. HungryG. morsitans(in East Africa at least) visit feeding grounds where animals are likely to be encountered; in so doing they are probably guided by a positive light reaction, which is reversed at high temperature (32o); they will follow artificial paths in absence of game.18. Feeding grounds are used less during the rains, when in East Africa flies are least hungry because the onset of hunger is slow, and they can survive 2 weeks without a meal. But in West AfricaG. morsitans submorsitansis hungriest in the cool, long‐grass season at the end of the rains, when large animals are scarce in its habitat and difficult to see.19. The numbers ofG. morsitans, G. stvynnertoni, G. palpalisandG. tachinoidescaught by a standard method give a fair index of true density from time to time, but not necessarily from place to place. Attraction ofG. pallidipesto man is usually very slight.20. MaleG. morsitansandG. stvynnertonilive about 4 weeks in nature, but life depends on temperature, and on saturation deficit at low or moderate temperatures. Fortunate individuals may survive 100 days; expectation of life is scarcely affected by age, since mean life is so much less than the possible span. Females live at least twice as long as males, and probably half the larvae deposited fail to become adult flies.21. A mean saturation deficit of 7 mb. is optimal forG. morsitans, and 4 mb. forG. tachinoides; the level of density during the following year is determined by conditions at the end of the rains, when in a dry year density will rise and in a wet year it will fall.22. Densities ofG. stvynnertoniandG. pallidipesfluctuate to a long‐term cycle which may or may not be associated with sunspots.23.G. morsitans, G. palpalisandG. tachinoidesare most active at about 27o, and inactive outside the limits 15½ and 41½o. Some species are active in the dusk or at night,G. pallidipesespecially on moonlight nights butG. austenioften in complete darkness. These two species are most active on the coast at high humidity, but inland on the arid plateauG. pallidipesis most active in dry weather. Attraction to man may be depressed by very high density of ungulates.24. There is some agreement between the proportion of teneral flies caught and the emergence rate. The proportion of females caught depends upon hunger, but also it is associated with the emergence rate because younger females are more active; younger males, on the other hand, are less active than older ones.25. The slow, coherent spread ofG. morsitansfly‐belts advancing into favourable country argues that wandering animals do little to assist their spread; and quantitative estimates of dispersal from an area of 4 X 4 miles showed much to‐and‐fro movement over short distances, but only 3 % weekly loss from flies passing off the scene altogether.26. In open grasslandG. swynnertoniwill follow cattle more readily in the wet season, but even in the dry season may remain with the animals up to 1½ hr. This species will exceptionally travel, apparently unaided, up to 2 miles in 3 hr.,

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1949.tb00574.x

出版商:Blackwell Publishing Ltd    

年代:1949

数据来源: WILEY

摘要:

SummaryThe iron bacteria, characterized by depositing iron compounds in a morphologically defined way, are a biological group, the knowledge of which has grown rather unmethodically as shown in the historical survey. Morphological, ecological, practical and biochemical investigations were never co‐ordinated.Taxonomically, the Chlamydobacteriaceae, the Gallionellaceae, and the unicellular iron bacteria are unrelated. The extraordinary variability of the first group has not been realized by most investigators, who have expected every appearance to be connected with a definite taxonomic form. Reversible modifications of a few species have been described under a multitude of names as different genera, species and varieties. It is proposed to go back to Kützing'sSphaerotilusas the oldest named genus, to which all the forms calledLeptothrix, Cladothrix Chlamydothrix, etc. also belong.Crenothrixis an exception, being another genus of the Chlamydobacteriaceae. With respect to the Gallionellacae, the definition of the species needs further investigation. The position in the unicellular forms is still worse.The ecology of iron bacteria is of special interest because it is connected with the iron cycle in nature. Iron is a physiologically essential chemical element, which may, oftener than any other, be deficient in natural habitats of algae and higher plants owing to its insolubility in the higher oxidation state. Iron‐depositing organisms are found only where oxygen has access, but near positions where chemical reduction is prevalent.Such conditions are difficult to maintain in experimental circumstances. Attempts made to replace ferrous by manganous compounds have failed because even in the presence of manganous compounds ferrous compounds are also required. Under natural conditions humus and other substances may help to keep iron in a suitable state by their reducing power and by their capacity to form more or less stable and at the same time soluble ferrous compounds. If such conditions were imitated in experiments, autotrophy would of course not be warranted. These are some of the reasons why the question has not yet been answered as to whether iron bacteria can grow without organic substances by utilizing the oxidation energy of iron compounds.New culture investigations have been undertaken to obtain pure strains from growths ofSphaerotilus, LeptothrixandCladothrix.All of them could be shown to belong to one or the other of two species:Sphaerotilus natansKützing andS. disco‐phorus(Schwers) nov. comb. From the former all the appearances described as different genera could be obtained by providing suitable conditions.S. discophorusbehaves in a similar way. Both can grow without producing inorganic sheaths. The sheaths when present are different in the two species, only those of the latter containing manganese. This admixture causes a characteristic brown hue, while the sheaths ofS. natansare almost colourless.Similar investigations are necessary in the other groups of iron bacteria, and on such investigations methodical and elaborate biochemical and morphological studies could be based.An index of names and synonyms with critical remarks is given, to show how many incomplete diagnoses have been made, and which of the species are likely to be maintained and which discarded. In order to facilitate the finding of information, the list of references to literature contains some titles not mentioned in the text.I am much indebted to Dr F. M. Haines, Queen Mary College, University of London, for correcting the man

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1949.tb00575.x

出版商:Blackwell Publishing Ltd    

年代:1949

数据来源: WILEY

摘要:

Summary1.Relation between nucleus and cytoplasm.Evidence is reviewed of interrelations between the interkinetic nucleus and the cytoplasm, together with recent findings concerning such interrelations between the female nucleus, the male pronucleus, and the karyocytoplasm of the fertilized starfish egg.2.Structural components of the protoplasm.Relatively stable and unstable structures (sol‐gel transformations) can be distinguished. Illustrations are given of cell nuclei, some of which are liquid (spinning glands) so that the progressive deposition of viscid material in the cytoplasm distorts the nucleus into a highly multilobulated shape. Other nuclei (dipteran salivary glands) react as solids from being packed with chromosomes. The boundaries of these chromosomes can be detected by injecting carbon particles which collect in narrow spaces between them.3.Miscibility of protoplasm with water.Cells can be injected with water which spreads through the cytoplasm. More is tolerated if the water contains monovalent salts, particularly potassium chloride.4.Internal osmotic pressure.The capillarity of spaces within a living cell, e.g. muscle fibre, complicates the evaluation of osmotic pressures when determining the freezing‐point of the living cell interior. The question also arises whether the freezing‐point depression of cellular extracts is valid for determining the osmotic pressure of the living cell.Funduluseggs, considered impermeable to water and to electrolytes, can be shown to be permeable to water by the fact that they develop high internal pressures when immersed in hypotonic solutions. The lack of swelling is due to the inelastic envelopes of the individual eggs.5.An electrolytic solution compatible with cytoplasm.The preparation of a solution approaching that of the interior of a myxomycete has been done by micro‐injecting solutions of varying constituents and ascertaining those exhibiting least toxicity.6.Extraneous coats.A study of the physical properties of the protoplasmic surface film is complicated by the presence of extraneous coats. The most generalized extraneous coat serves as an intercellular cement, the consistency of which is conditioned by the pH and the proportion of calcium and sodium in the medium. The permeability of multicellular membranes is affected by the condition of this cement.7.Hyaluronidase.A hyaluronidase‐like substance from sea‐urchin sperm dissolves the jelly coats of the eggs, but has no effect on the intercellular cement. In this way it resembles the hyaluronidase of mammals which dissolves the mucinous collagen but not the intercellular cement.8.The ‘plasma membrane’. Removal of extraneous coats leaves behind a bounding film on the protoplasm. This film has flowing characteristics and is liquid in the presence of calcium in the environment.9.The hydrogen‐ion concentration of the cell interior.The determination is valid for the continuous aqueous phase of protoplasm. The pH virage of this is slightly, if at all, affected by the presence of the living protein which is relatively inert. Intracellular vacuoles have their own pH values which are independent of the pH of the protoplasmic aqueous phase. Neutral red, a chloride of a coloured base, accumulates in acidic vacuoles and stains fatty globules, while phenol red, a sodium or potassium salt of coloured acid, colours the cytoplasm diffusely and only later tends to accumulate in alkaline vacuoles and in the nucleus which is alkaline.Therefore, in a consideration of the pH of protoplasm it is essential to take into account various factors. Lack of such consideration and the fact that certain regions in the cell are affected by variations in external pH have given rise to confusion in the literature. The only stable region which is well buffered and which, as long as the cell is alive, maintains a constant pH value, is the continuous aqueous phase of protoplasm, that of the cytoplasm being in the close neighbourhood of pH 6–8 and that of the cell nucleus, 7‐6‐7‐8.10.The action of salts on the interior of protoplasm.Reactions to the micro‐injection of salts indicate that the proteins in protoplasm are predominantly on the alkaline side of their isoelectric points. Calcium induces coagulation, while sodium and potassium have a dispersive action. In some cases, cell inclusions exist which are agglutinated by sodium chloride. This feature may lead to erroneous conclusions in centrifugation experiments in which the degree of sedimentation of visible granules is used as a criterion for viscosity.11.Living and dying protoplasm.Living proteins are relatively inert to chemical interaction. Upon the initiation of cytolysis the interactions become prominent accompanied by denaturation of the proteins. The acid of injury may be explained by the increase of ionizable carboxyl groups resulting from the conversion of protein macromolecules to low molecular weight proteins.12.Relation of structure to ‘one‐way’ permeability.The cells of the renal proximal tubule in tissue culture lose their ‘one‐way’ permeability to phenol red when they grow out as flattened sheets. They regain it on becoming orient

ISSN:1464-7931    

DOI:10.1111/j.1469-185X.1949.tb00576.x

出版商:Blackwell Publishing Ltd    

年代:1949

数据来源: WILEY