摘要:

SUMMARY1Octopuses readily learn not to attack a crab shown with a square of one size, while continuing to attack a crab shown with a larger or a smaller square.2They can also learn to attack when a square of one size is shown, food being given as reward, but not to attack squares of other sizes if the attack results in a shock.3An octopus can learn to attack a square of 4 cm. but to avoid squares of 2 and 8 cm.4A square of 4 cm. presented at half the usual distance is not confused with a square of 8 cm.5By the same method it was shown that octopuses can make distinet reactions to certain figures that differ only in shape but not in area and length of outline, for instance rectangles and squares, or rectangles turned up at the ends, which differ in extent in vertical and horizontal directions.6They can also make distinct reactions to a rectangle according to whether it is shown vertically or horizontally, or to a square shown in various orientations in relation to gravity.7The accuracy of forecasting becomes less as an octopus is presented with situations that are more nearly similar.8Distinct reactions were also set up to crosses and squares and, less accurately, to figures with internal differences.9No clearly distinct responses could be set up to a square and a circle.10Octopuses trained to give distinct reactions to two different figures give the appropriate reaction to smaller figures, except when the differences are slight.11Change of other attributes of the situation, for example by moving to another tank, may disturb the animal's performance but does not destroy the memories.12After anaesthesia with urethane there is a period in which attacks are not made on either figure (though crabs are normally taken). Later, response to the positive figure returns but the negative is not attacked. The memories have therefore survived the treatment. Anaesthesia produces greater disturbance of performance if the two situations are nearly alike or involve attacking the larger rather than the smaller of two figures.13After removal of the vertical lobes octopuses continued to attack the figure that had been associated with food. They showed some attacks on a “negative” figure but when shocks were given they again ceased to attack this figure.14The animals without vertical lobes were unable to retain memories preventing attack on crabs from which shocks had been received (Boycott&Young, 1955 b). The vertical lobes are therefore necessary for the reversal of well‐established memories, such as that leading to attacks upon crabs. They play a part in setting up memories that prevent attack upon previously unknown figures but are not essential for the retention of such mem

ISSN:0370-2774    

DOI:10.1111/j.1096-3642.1956.tb00451.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

摘要:

SUMMARYBy means of trapping experiments, the times of activity ofApodemus GlethrionomysandMicrotuswere studied in the field mainly in areas where populations had been marked. The results serve to compare field observations with data already published from controlled laboratory experiments.ApodemusandClethrionomys,living in the same habitat, showed a wellmarked nocturnal‐diurnal rhythm. In both species their twenty‐four hour cycle had its peak around dusk and dawn. Except that there was no two hour period of complete inactivity at Silwood, results in the autumn and winter forApodemuswere similar to those of Elton, Ford, Baker&Gardner (1931). A peak at dusk was followed by a lull and then by a secondary peak persisting until dawn. In the spring and summer, however, when the hours of darkness were short there was no pronounced second peak at dawn.The feeding cycle ofClethrionomysappeared to be of about two hours duration. As many as 34‐9 per cent of the males and 22‐9 per cent of the females visited traps at each two hourly trapping period in any one day. The twenty‐four hour rhythm ofClethrionomyshad, as well as peak activity near dusk and dawn, a further peak in the afternoon. However, when the daylight hours were long, evening activity had often subsided sometime before dusk. In areas whereApodemusandClethrionomyswere both present there were larger catches of the species that had first chance of entry, even when the number of the traps appeared to be excessive. Only a few persistent trap visitors amongApodemusbroke their strictly nocturnal habit, such animals being normally only a small percentage of the total population (Brown, 1954).Apodemustook some weeks to range into unoccupied grassland, but once there remained until forced out by high Microtus populations.Field experiments onMicrotusat Silwood confirmed laboratory tests made by Davis (1933). The animal showed a well marked peak of activity at dusk and dawn associated with its twenty‐four hour rhythm. It was active both day and night, showing a feeding rhythm of about two hours, but with more activity during the night than during the day.Except for periods of prolonged frost the three species showed some activity in all weathers. Rainfall might delay appearance above ground or send more animals into the traps for shelter. In heavy rain activity continued to be normal under shelter, but was much reduced in exposed positions.Factors affecting peak activity including experiments on internal physiological rhythms have been considered. Discussion includes also the possible influence of:‐availability of insect food, refection, naturally increased water supplies morning and evening and the avoidance of periods when predatory activity is facilitated, as for example on moo

ISSN:0370-2774    

DOI:10.1111/j.1096-3642.1956.tb00452.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

摘要:

SUMMARYThree new species of Cetotheres,Mauicetus lophocephalus, Mauicetus waitakiensisandMauicetus brevicollisare described from the Lower Oligocene of New Zealand. The greater part of the skull of one of these is present and it seems to be considerably the oldest Cetothere skull known. It appears to be primitive in that, although the supraoccipital shield extends as far forward as it does in many Miocene Cetotheres, the nostril is very anteriorly placed, the temporal fossae are longer than broad and there is a long sagittal crest in the cranial region. There is therefore a considerable gap between the supraoccipital and the nasals, unlike the condition usually seen in the Mysticetes. A gap is present here in other early whales, but only in the Archaeocetes is it occupied by a sagittal crest.

ISSN:0370-2774    

DOI:10.1111/j.1096-3642.1956.tb00453.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

摘要:

SUMMARY1In young monkeys and apes, and human skulls of all ages, the cranial attachments of the temporalis and nuchal muscles are completely separate.2As the permanent teeth erupt, the facial skeleton grows much faster than the cranium, and the correlated development of the temporalis and nuchal muscles results in the formation of bony crests in the occipital region (nuchal crests) and sometimes also in the mid‐sagittal line of the skull (sagittal crests).3The crests are most powerfully developed in the gorilla, especially in males, where a nuchal crest may eventually become a uniform shelf of bone as much as 4 cm. wide. A sagittal crest begins to form in the region immediately anterior to the inion. It is present in all males, and may be as much as 5 cm. high. It is found in only about two in every five females.4In the adult chimpanzee, the nuchal shelf is formed only in the middle part of the arc between the mastoid and inion, and even in males does not project more than 0–6 cm. A sagittal crest is never found in female chimpanzees. A sagittal ridge or small crest develops in about one male in six. It begins to form mid‐way between the bregma and lambda.5In the orang‐utan, the nuchal crest varies in its development. Occasionally it forms a continuous shelf from mastoid to mastoid, and sometimes it is present in only the middle part of the arc between the mastoid and the inion. A sagittal crest develops in up to seven out of every ten adult males, but in only about one adult female in twenty. It begins to form in the region mid‐way between the bregma and lambda.6In the gibbon the nuchal crest seldom projects more than 0–1 or 0–2 cm., and extends over only the middle part of the arc between the mastoid and inion. Even in adults, and in contrast to the condition found in most apes and monkeys, the temporal lines are often closest together in the region of the bregma. Very rarely they meet to form a sagittal ridge in this region.7In the adult white‐nosed monkey, the nuchal crest occupies at most only the middle third of the arc between the mastoid and the inion. A sagittal crest is present in about one adult male monkey in ten, but never in adult females. It may develop near the bregma, near the inion, or at both points simultaneously. It extends along the whole length of the sagittal suture in less than one male skull in twenty.8In the adult male baboon, the nuchal shelf may extend uninterruptedly from mastoid to mastoid, and may project as much as 0–5 cm. In some males and in all females it extends for only a short distance behind the mastoid. The sagittal crest forms in the region immediately anterior to the inion in practically all adult males. In the female the temporal lines may touch immediately anterior to the lambda, but a true crest does not develop.9In the woolly monkey, the nuchal crest is weakly developed behind the mastoid. Even in adult males it seldom extends for more than 2 cm. and projects at the most for 0–05 cm. In some adult females not even a nuchal crest is formed. No sagittal ridge or crest was found in any of the skulls of this type of monkey that were examined.10The growth processes underlying the formation of the cranial crests are similar throughout the Primates, variations between different species resulting from differences in the relative speed of growth and in the point at which growth stops. Thus:(a) In all primate species the posterior fibres of the temporalis muscles grow more rapidly than the middle and anterior groups, and consequently first approximate to the upper advancing edge of the nuchal muscles at a point between the mastoid and inion.(b) In young animals in which only the milk teeth are in place, the temporal lines are closest together immediately posterior to the glabella. Subsequently, however, as the middle fibres of the temporalis muscle grow more rapidly than the anterior ones, the point of least separation moves backwards to the region of the bregma. Further growth may result in their meeting in the mid‐sagittal line of the skull, at a variable point between the bregma and lambda to form a sagittal crest.1In both fossil and living man, the temporalis and nuchal muscles do not approximate, and neither a nuchal nor a sagittal crest is ever formed.2The evidence for the three available specimens ofParanthropus crassidens,in which a sagittal crest is present, suggests that the cranial crests of the Australopithecinae developed according to the general pattern which prevails i

ISSN:0370-2774    

DOI:10.1111/j.1096-3642.1956.tb00454.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

摘要:

SUMMARY1The bodies of two yearling Grey Seals from a colony living in the south of the Isle of Man were dissected, their gut contents examined and their parasites identified.2The identifiable stomach contents of the bull yearling consisted of many fish otoliths (mainly belonging toGadus luscus)and the remains of bottomfeeding crustaceans. The identifiable stomach contents of the yearling cow were a few fish otoliths (two of which belonged toGadus virens)and tufts of mainly algal detritus.3The literature on the parasites of Grey Seals has been reviewed.4One yearling seal bore seven and the other five species of internal and external parasites. Their distribution in the body has been described. The slightly older cow seal suffered from a considerably heavier infection of gut parasites than the bull yearling.5The intestinal trematodeCryptocotyle lingua(Creplin) has apparently not been recorded before for the Grey Seal.

ISSN:0370-2774    

DOI:10.1111/j.1096-3642.1956.tb00455.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

ISSN:0370-2774    

DOI:10.1111/j.1096-3642.1956.tb00456.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY