ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1941.tb08469.x

出版商:Blackwell Publishing Ltd    

年代:1941

数据来源: WILEY

摘要:

Summary.(1) Details (with photographs) are given of the habit of brooding the young on the perch in the PheasantBheinardia ocellataand the PigeonChalcophaps indica.(2) This habit is best developed in nidifugous forest‐dwelling species where the young roost in branches from an early age, and where only two young are produced. The limitation of the number of young to two facilitates brooding on a linear support like a branch.(3) It appears to be a diagnostic character of the subfamilyArgusianinse.(4) It may occur in other forms as well: (a) in nidifugous species with more than two young, such asOallus, (b)in nidicolous types such as Pigeons(Chalcophaps

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1941.tb08470.x

出版商:Blackwell Publishing Ltd    

年代:1941

数据来源: WILEY

摘要:

Summary.(1) A brief description is given of a male hybrid betweenChrysolophus amherstiasandLophophorus impeyanus, two markedly different genera of thePhasianinas.(2) The chief point of interest is the almost complete disappearance of the striking colours and patterns of the two parents, the hybrid being almost entirely black with no or very limited iridescence.(3) The crest‐shape of the Amherst is dominant, while the facial skin of the hybrid resembles that of the Impeyan parent.(4) The cape of the Amherst, which is wholly unrepresented in the Impeyan, is present in the hybrid but is reduced in length and feather‐breadth, and is not developed on the anterior margin of its normal area; it has not been seen to be spread in display.(5) The tail is roughly intermediate in length and shape.(6) The body‐build inclines somewhat towards the Amherst parent, though the size is intermediate. The Impeyan habit of digging with the beak is dominant over the Amherst habit of scratching with the

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1941.tb08471.x

出版商:Blackwell Publishing Ltd    

年代:1941

数据来源: WILEY

摘要:

Summary.A technique for estimating the pre‐natal mortality in the vole,Microtus agrestis, by palpating the embryos, is described. The results obtained from a laboratory stock of voles show a mortality of at least 21‐07 per cent.14–20 per cent, of the young born alive die during the 14 days between birth and weaning, giving an accumulated loss of at least 32‐28 per cent, for the first 35 days of existence.The sex ratio at weaning was 50–89 2‐22 mal

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1941.tb08472.x

出版商:Blackwell Publishing Ltd    

年代:1941

数据来源: WILEY

摘要:

Summary.1. The quantitatively outstanding effects of beryllium on embryonic development may be correlated with the rarity of this element in nature.2. Qualitatively the effects are such as may be produced by other chemical agents in appropriate concentration and by other experimental means. The most notable are: exogastrulation, spina‐bifida, axial defects in general, hemicephaly and microcephaly.3. Situs inversus of heart and viscera has not previously been produced in Amphibia by chemical means, but no doubt is part of the general complex of effects.4. The common action of all reagents would seem to be essentially one of inhibition, acting differentially on different parts of gradients of activity in the embryo.5. There is evidence for the existence of three main gradients in the embryo, in the three dimensions of space. Two gradients alone cannot explain the organization of the Vertebrate embryo.6. The form and orientation of the gradients changes during normal development. This is reflected in the complexity of the experimental effects produced.7. The question of the evolutionary significance of the “mosaic” stage of development is raised.8. Rhythms in susceptibility to external agents during development are revealed.9. Examples of dependent and of independent differentiation are noted.Summary.1. Beryllium salts have a powerful inhibitory effect on regeneration in Amphibia. No other agent used had a comparable effect, which might indicate the chemical mechanism of the effect.2. Inhibition of regeneration with beryllium provides a valuable means of investigating the problems of regeneration and growth. The present experiments indicate that:–(a)A factor produced very locally at the cut surface at the time of operation is largely responsible for regeneration. It is this factor which is so rapidly inactivated by beryllium treatment.(b)There is evidence of a second factor concerned in regeneration in Amphibia. This appears to emanate along the axis, in the tail.(c) Partial inhibition affects both rate of regeneration and final size of the regenerate. This supports the indication that regeneration does not depend on a single factor.(d)Partially inhibited limbs have frequently fewer digits than normal.(e) The stump of inhibited limb‐buds develops as a mosaic(i. e., does not regulate).(f) Normal powers of regeneration vary considerably in different animals.(g)The “wound factor” may possibly show affinities with the “organiser” substance of embryolo

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1941.tb08473.x

出版商:Blackwell Publishing Ltd    

年代:1941

数据来源: WILEY

摘要:

Summary.1. The viability ofPandalus borealisat temperatures from ll‐5o‐20‐3oC. has been studied. Thermal death occurs at 11‐5oC.2. When the mean lethal exposure to various temperatures is plotted against temperature two curves are obtained, meeting at a critical temperature of about 16‐5o. The temperature coefficients Q10, ft andmhave different values above and below this critical temperature. This indicates that the causes of death are different above and below 16‐5oC.3. When animals are transferred suddenly from 5–6oC. to a high temperature (19‐2oand 20‐3o) they die after a shorter exposure to that temperature than when the change is made gradually over a period of one hour.4. The rate of scaphognathite beat varies not only with the activity of the animal but also with its previous history; the disturbance due to catching increases the rate enormously, and the effect of this lasts 2–3 days.5. The rate of scaphognathite beat increases not only with rising temperature, but also with the length of time the animal is exposed to a high temperature; it is suggested that this unusual behaviour may be due to a decline of inhibition of

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1941.tb08474.x

出版商:Blackwell Publishing Ltd    

年代:1941

数据来源: WILEY

摘要:

Summary.(1) The injection of a thyreotropic fraction of the mammalian pituitary in ammoccete larvse ofLampetra planeriproduces a rapid and marked decrease in body‐length, and also histological changes in the endostyle. These changes were found to be reversed if further injections were given.(2) No other signs of metamorphosis were observed in the injected animals.(3) Monthly samples of the ammoccete population in the river Sarno, Naples, Italy, indicate that the larval life of lampreys in that region may extend for not less than two years and not more than three years approximately.I should like to thank Dr. R. Dohrn for the facilities afforded me at the Stazione Zoologica, Naples. The pituitary extracts used in the experiments were kindly supplied by Dr. A. S. Parkes and the British Medical Research Council. I am grateful to Professor Goodrich, F.R.S., and J. Z. Young, M.A., for reading the paper and for helpful criticism. I am also grateful to Angelo Sessa for his help in making the lamprey samples in the river Sarn

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1941.tb08475.x

出版商:Blackwell Publishing Ltd    

年代:1941

数据来源: WILEY

摘要:

Summary.1. The flagellum is an active unit in so far that it generates at least a part of its own energy irrespective of the attached cell.2. In all cases so far examined the impulses or waves start at the base of the flagellum and not at the tip.3. As a wave passes along a flagellum there is always a certain amount of rotation of the tip of the flagellum.4. A method for determining both the rate of swimming of the organism and the rate of beat of the flagellum is described.5. The rate of transmission of an impulse along a flagellum has been measured. InEuglena viridisit was found to be of the order of 810 μ per sec. or well under a foot per minute, which is almost infinitely slow compared with the rate at which an impulse passes along a nerve.6. The term “Tractellum” is discussed and its use should be discontinued. Tractella are simply ordinary flagella attached to the front end of the organism, the impulse starting at the base and not at the tip.7. The rotation of the organism itself is due to the plane in which the flagellum beats. A high rate of beat of the flagellum does not necessarily imply a high rate of rotation of the organism.8. The mechanics of the flagellum are discussed, but no attempt is made to discuss the nature of the movement within the flagellum though the slow rate of impulse is highly suggestive that it is a surface action comparable to heatconductionrather than radiation.9. Flagella attached to the hinder end of the organism and pushing it through the water present certain mechanical difficulties and occur in nature rather seldom. The more stable mechanism is for either a single flagellum or a pair of flagella to be attached to the front end to push the organism through the w

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1941.tb08476.x

出版商:Blackwell Publishing Ltd    

年代:1941

数据来源: WILEY

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1941.tb08477.x

出版商:Blackwell Publishing Ltd    

年代:1941

数据来源: WILEY