摘要:

Summary..(1) To test the hostility reactions of Black‐headed Gulls(Larus r. ridibundus)the following were employed:–Stuffed mounts, one in summer and one in winter plumage; a dead bird in summer plumage, propped up; the same bird decapitated; and its isolated head.(2) Hostility reactions were immediately elicited by both the mounts, provided they were within a certain distance from a nest. This territorial radius averaged about 3‘ 6“, varied with the temperament of individual birds, and with the temporary state of one and the same bird. No hostility was shown by occupants of more distant nests, nor by any birds when the mount was set up on neutral ground away from the nesting area.(3) Hostility was also evinced towards the dead bird, but, presumably owing to its less natural pose, the reaction was less extreme.(4) In all these cases hostility was chiefly shown by pecking the back of the head. The feet were also used while flying over to attack the back, and occasionally other parts than the head were pecked. It is uncertain whether the head was less singled out for attack in the winter than in the summer plumage mount.(5) No attacks were made upon the decapitated dead bird, in spite of its causing obvious anxiety and preventing return of birds to the nest near which it was placed.(6) The isolated head, when set up on a skewer, was attacked, in this case being pecked on the beak as well as from behind. On one occasion when it fell into a nest with eggs, it was pecked lightly and then treated like an egg and brooded.(7) It is concluded that two factors compete in eliciting hostility:–(a)Resemblance in form and pose to a normal individual; (6) the dark‐brown head of the breeding bird. Either alone is operative, but with both together (summer plumage mount) the result is possibly more intensive, and probably more specific, the dark head acting as a directive for the attack.(8) Suggestions are made for further experiments to test and amplify these

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1940.tb08455.x

出版商:Blackwell Publishing Ltd    

年代:1940

数据来源: WILEY

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1940.tb08456.x

出版商:Blackwell Publishing Ltd    

年代:1940

数据来源: WILEY

摘要:

Summary..1. The nature of the colour changes shown bySepia officinalisL. in different environments is discussed.2. Several patterns in the coloration of the animal, each appearing under certain specific conditions of stimulation, are described.3. Each pattern is formed by a pattern of expansion and contraction of the chromatophores, supplemented by reflection from the immobile iridophores which lie below them.4. The state of expansion of each chromatophore is determined by its musculature, which is under nervous control; and therefore each colour pattern is a manifestation of a pattern in the process of excitation of the chromatophore motor neurons in the central nervous system.5. In no other Cephalopod thanSepiahave such colour patterns been described, and they form a complex and highly developed system of protective coloration, adapted to the conditions under whichSepialives.6. The types of protection afforded by the colorations are discussed. Cryptic patterns are found affording protection through obliterative shading, close environmental resemblance, and striking ruptive patterns.7. Concealment is made more effective by the animal's ability to change its coloration from one pattern to another in times as short as two‐thirds of a second.8. Certain of the colour changes probably protectSepiaby virtue of their great rapidity for, like any sudden change in the visual field, they produce a flight reaction in the predator.9. Such rapid change of colour thus forms a new category in the classification of the means by which colour can afford protection to animal

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1940.tb08457.x

出版商:Blackwell Publishing Ltd    

年代:1940

数据来源: WILEY

摘要:

Summary.The interstitial cells of the testis ofPteropus geddieiwere found to be most numerous and their volume to be greatest when copulation occurs and for the three months preceding this. It is therefore supposed that the greatest quantity of male hormone is elaborated at this time, October‐February, when the bat is social and sexual.From March to June there is moderate glandular activity, the behaviour of the bat being social and asexual.In July and August interstitial activity is at its minimum, and the bat is solitary and asexual.There is a significant seasonal variation in the interstitial tissue of these bats, living in a remarkably constant tropical climate; although the variation is less pronounced than that found in British Wood Mice.It is suggested that the male hormone may to some extent control the purely social behaviour ofPteropu

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1940.tb08458.x

出版商:Blackwell Publishing Ltd    

年代:1940

数据来源: WILEY

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1940.tb08459.x

出版商:Blackwell Publishing Ltd    

年代:1940

数据来源: WILEY

摘要:

Summary.1. The aim of the paper has been to show how far differences in proportions may safely be used in systematic grouping. The use of percentage sizes is unsatisfactory since they generally change with absolute size, and Huxley suggested the allometry formula as a basis for analysis. But no study has been made of the best statistical methods for(a)discovering the nature of the growth‐relationship between two organs from small samples, (6) estimating the most probable values of Huxley's growth‐coefficients and comparing these in different samples.2. Difficulties in (a) and(b)are discussed. While it is usually impossible to determine the nature of the growth‐relationship from small samples, the systematist can make use of the allometry formula if the points appear to show a linear trend when plotted on a double logarithmic grid. Reasons are given for supposing the normal regression methods applied to the logarithms of the measurements to be the best way of estimating the values of the growth‐coefficients.3. To illustrate the methods, measurements were made of lengths of maxilla;, nasals, and cranium in samples of the skulls of the three genera of Xenarthrous Anteaters,Myrmecophaga, Tamandua, andCyclopes.Their adult facial indices and total skull‐lengths are:–Myrmecophaga: facial index=l‐6, skull‐length 36 to 38 cm.Tamandua:facial index=0–80, skull‐length 13 to 14 cm.Cyclopes: facial index =0–5, skull‐length up to 5 cm.The systematic problem is “Do genetic differences directly affecting relative face‐length intervene between the three genera, or are the laws of relative growth in face‐length the same throughout ?”4. Convenient changes in notation are suggested and the regression formulae described. Calculated values of a and their standard errors are given Table I. p. 59.t‐tests applied to these suggest thatMyrmecophagahas a higher relative growth‐rate in face length than the other two genera, which do not differ very much. The initial growth index and its standard error are, however, found to be quite useless for purposes of comparison.5. A better method of analysis is proposed. This consists in comparing the fit of a single line, separate lines, and parallel lines to the samples by an analysis of Residual Variance. Comparison of parallel lines through the sample means and separate lines will test differences in slope, and comparison of a single line with parallel lines will test differences in other factors, here termed “positional.”6. These tests show no differences between the two samples ofTamanduameasured by different observers. Applied to the three genera they show clearly that allometric differences intervene between them, both slope and positional differences being significantly large. Further tests show no significant differences in slope betweenTamanduaandCyclopes, while positional differences between them appear only for the allometry of the maxillaæ. If this means that the snout has the same average relative growth‐rate in both genera, then calculation shows thatTamanduahas on the average maxillae 1–36 times and nasals 1–09 times as long asCyclopeswith the same cranium length. Difficulties are discussed in interpreting the test for positional differences when slope differences are significant.7. Size‐increase in the skull ofMyrmecophagacompared withTamanduaappears to have been concentrated in length. The former has relatively a much slimmer rostrum and more sharply‐pointed posterior projections to the nasals and anterior projections to the frontals.8. Most of the main differences between the skulls ofCyclopesand the two larger genera are probably the result of the marked size‐differences. The reduction in facio‐cranial flexure and sharpness of the dorsal edges to the orbits, and the loss of the eoronoid process, which occur in the larger genera, may be due to this factor. The systematic value of these differences is therefore doubtful, and the evidence for classifyingCyclopesin a separate subfamily after Winge, or in a separate family after Pocock, is unsatisfactory. A return is proposed to the original classification of the group as three separate genera forming the family Myrmecophagidse.9. These anteaters present the unusual case of a positive correlation between the rela

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1940.tb08460.x

出版商:Blackwell Publishing Ltd    

年代:1940

数据来源: WILEY

摘要:

Summary.The food of salmon parr in the Dee and its tributaries has been studied for two years. Comparison of stomach‐contents with the results of field collections shows that the fishes are indiscriminately carnivorous, and that their diet varies strictly in accordance with the number and relative accessibility of species present in the rivers. The sub‐äerial element in the food is important, especially in autumn, when leaf‐eating tree‐parasites fall into the rivers as the leaves decay and are swallowed in considerable numbers. Encouragement of the growth of riparian trees and shrubs is thus desirable.There is a marked seasonal cycle in feeding, which accurately corresponds with the records of fluctuations in growth derived from scale‐readings. This seasonal cycle seems to be directly dependent upon the life‐histories of the various food‐organisms, which determine their availability to the fishes: in the opinion of the writer there is no evidence of loss of appetite at any season, but merely of variations

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1940.tb08461.x

出版商:Blackwell Publishing Ltd    

年代:1940

数据来源: WILEY

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1940.tb08462.x

出版商:Blackwell Publishing Ltd    

年代:1940

数据来源: WILEY