摘要:

SUMMARYSeven more oriental species (two of which are considered to be new to science) have been re‐examined and drawings made of the parts essential for identificatio

ISSN:0370-2774    

DOI:10.1111/j.1096-3642.1955.tb00600.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

SUMMARY1Four hundred and nine skins of common shrews were preserved, of which sixty‐eight showed some stage of moulting. Examination of these specimens revealed that the shrew moults twice in its lifetime; in the autumn of the year of birth the juvenile coat is replaced by longer darker fur; a spring moult replaces the winter coat with shorter fur of the same colour. Thus adult common shrews are generally darker in colour than juveniles.2Black pigment appears in the skin before moulting, and disappears as the hair grows.3Fifty‐two per cent of the Wytham shrews had some white hairs upon the ears, and 20·9 per cent of males and 17·4 per cent of females possessed predominantly white ears,4The scruff bore a scar or patch of white hairs in eleven animals, all of which were pregnant or parous females. The term “copulation scar” is suggested as a more suitable term than “grey patch”.5White‐tipped tails were noted in 3.7 per cent of the skins, with a statistically significant correlation

ISSN:0370-2774    

DOI:10.1111/j.1096-3642.1955.tb00601.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

SUMMARY1Certain characters of the skins and skulls of (a) the European polecatPutorius putorius putorius, (b) the Asiatic polecatPutorius putorius eversmanniand (c) the domestic ferretPutorius putorius furohave been compared.2The ferret resembles the European polecat more closely than the Asiatic in:(a) the extent of the black area of the tail;(b) the overall size and shape of the skull;(c) the position of the postorbital constriction;(d) the proportions of the pre‐ and post‐zygomatic parts of the skull:(e) the shape of the nasal bones;(f) the hooking of the hamular process.3It resembles the Asiatic polecat more closely than the European in:(a) the proportion of individuals in which the frontal band is continuous;(b) the degree of constriction of the postorbital region.4The skull of the ferret is more variable than that of either the European or Asiatic polecat.5The data are inadequate to decide whether or not the differences between the ferret and European polecat are too great, to permit the view that the ferret of today is merely the descendant, of a domesticated variety of European polecat.6It is suggested that the changed breeding system and selective forces which operate on the captive animal, may be conducive to the origin of differences of this t

ISSN:0370-2774    

DOI:10.1111/j.1096-3642.1955.tb00602.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

SUMMARY1A description is given of the scales ofEpiceratodus, ProtopterusandLepidosiren, and the associated soft tissues.2InEpiceratodusthe scale still shows considerable differentiation, and its parts can be related in some degree to those of the ancestral cosmoid scale. The cosmine layer has disappeared, but the outer calcified layer probably represents the remains of the lacunar layer, and the inner laminated layer may represent the isopedine.3InProtopterusandLepidosirenthe scales are much simplified but their structure can still be understood through that ofEpiceratodus.Direct, attachments between the posterior part of the scale and a superficial connective tissue layer are present in all, and the incomplete type of pocket in which the scale lies differs only in detail.

ISSN:0370-2774    

DOI:10.1111/j.1096-3642.1955.tb00603.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

SUMMARYThe gut ofArenicola marina, is a long straight tube stretching the entire length of the worm. It can be divided into five regions:(a) the proboscis, containing the buccal mass, pharynx and postpherynx,(b) the oesophagus, divided into the jugular, muscular and glandular regions.(c) the stomach, consisting of the cardiac and post‐cerdiac regions,(d) the intestine end(e) the rectum.Four layers are distinguishable in the gut wall, though the thickness and the types of cells found in the innermost one vary from region to region. They are:(i) the outer peritoneal covering,(ii) a longitudinal muscle layer,(iii) a circular muscle layer and(iv) an inner epithelium.There is a system of ciliary tracts, which in the glandular region of the oesophagus is associated with the longitudinal ridges of the lining epithelium; and which consists of the ciliated ventral groove and lateral tracts arising from it in the post‐cardiac region of the stomach, the intestine and the rectum. There are isolated patches of cilia on the walls of the cardiac region of the stomach. Movement of the cilia in these tracts is believed to keep the contents of the stomach mixed and in suspension, thus ensuring that the food particles are brought into contact with the entire epithelium. The cilia also assist the passage of food through the gut, although this is mainly brought about by the rhythmic contractions of the body wall impinging upon the latter. The oesophagus is capable of a considerable amount of muscular activity and initiates some of the gut movements.Parts of the blood system of the animal lie in close proximity to the gut and as the blood system plays a part in digestion, its arrangement and the circulation of blood have been described.Food consisting of beach sand passes through the trunk gut, i.e. the proboscis, oesophagus, stomach and intestine, to the rectum in about fourteen minutes in an actively feeding worm. Food is taken into the oesophagus from the base of the funnel of the burrow by the constantly everting and inverting proboscis, without any preliminary sorting. It is temporarily stored in the muscular region of the oesophagus, but eventually it passes to the stomach through the glandular region of the former, where mucus and a little enzyme material is poured onto it by the unicellular glands in the walls. At the junction of the oesophagus and the stomach there are the openings of the oesophageal pouches, the secretion from which contains mucus and Qestive enzymes. While in the stomach food particles in the sand are digested both intra‐ and extra‐cellularly, the epithelial cells engang the food particles thus leaving the lumen of the gut filled with the large residual mass of indigestible, mostly siliceous, material. These food particles are taken from the epithelial cells by amoebocytes, which while digesting them, wander to all parts of the body in the blood and coelomic fluid. The indigestible remains of these particles are deposited by the amoebocytes in the epidermis, peritoneal cells, intravasal tissue, coelom and in the lumen of the gut.pH values are given for different parts of the gut, only that of the stomach (pH 5·4–6·0) differing appreciably from neutrality. Changes in pH affect the viscosity of the mucus, which is least viscous in the stomach where the pH is lowest. This aids the cilia and the movements of the gut in keeping the contents of this region in suspension. Elsewhere in the gut, the mucus is more viscous and acts as a lubricant, protecting the gut wall from the abrasive action of the sand grains.An actively feeding worm defaecates at intervals of approximately forty‐five minutes. During each defaecation cycle, the intestine absorbs 2·67 gm. of water. This is a considerable quantity for a worm weighing about 6 gm. (excluding tail). The reason for this absorption of water from the gut contents is not known, but it may be linked with the necessity to produce coherent faeces, which can be ejected well outside the exit of the burrow and so not interfere with the respiratory and feeding activities of the worm.High ambient temperatures (water temperature 28°C.) do not affect the rate of defaecation, and, therefore, neither do they presumably affect that of feeding. These rates are influenced to a considerable extent by the water content of the sand in which the burrow of the worm lies.The gut ofArenicola marinais adapted anatomically and physiologically to obtain the maximum extraction of the very small proportion of organic matter from the beach sand, which is its diet. The earthworm resemblesArenicolain that its diet also contains a large inorganic indigestible portion and as is to be expected, there is considerable similarity in the physiology of digestion in the two animals. In as far as the digestive processes of other sand eating animals are known, e.g. other oligochaetes, the spatangoids, and holothurians they all appear to share withA. marinathe characteristic of a large amount of digestion occurring intracellularly in wandering amoebocytes, thus leaving the gut lumen free to deal with the vast quantities of indigestible sil

ISSN:0370-2774    

DOI:10.1111/j.1096-3642.1955.tb00604.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

SUMMARY.1A survey has shown that protohaemochromogens in the gut lumen are widely distributed in Mollusca and Polychaeta, but are not widespread in Crustacea. These compounds were always found in highest concentration in the anterior part of the gut.2All the Polychaeta examined, with the exception of two species of Chaetopteridae, were found to have a gut protohaem compound, and in several species this was shown to be methaemoglobin, or an undentified compound which may have been haematin but was not 2 haemochromogen. Haemochromogens were of more frequent occurrence in tubicolous than in free‐living Polychaeta.3In several species of Polychaeta an inverse correlation was established between the concentration of gut haem (as haemochromogen or unidentified haem) and that of the respiratory pigment in the blood (whether haemoglobin or chlorocruorin).4The survey has given no indication of the factors governing the presence or the nature of the particular haem compound in the gut, but there is evidence that these compounds are derived from the tissues of the animal in which they are found rather than from the food.5The variation in the concentration of haemochromogen in the gut ofHelix aspersaandDaphnia magnahas been studied in the field and in the laboratory.6The concentration has been found to vary little with the nature of the food, although inDaphniaan external factor of unknown nature has been found to be necessary for the maintenance of a high concentration in mature animals.7The amount of helicorubin in the crop ofHelixhas been shown to vary with the activity of the animals, and with the state of digestion of the food.8Evidence has been put forward that helicorubin is reabsorbed from the gut ofHelix, and that it is not lost from the body.9The amount of daphniarubin in the anterior part of the gut ofDaphniahas been found to vary with the activity of the gut, but the chief cause of variation is the concentration of body haem. Direct and inverse correlations with the haemoglobin concentration in the blood have been established under different condition

ISSN:0370-2774    

DOI:10.1111/j.1096-3642.1955.tb00605.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

SUMMARY.1Oligochaete worms believed all to be representative of one species ofChaetogaster, quite probablyC. limnaei, were found in four Merent kinds of fresh‐water snails, namely,Biomphalaria, Physopsis, BulinusandMelanoides.2Amphistome, echinostome, longifurcate and brevifurcate cercariae were observed in the intestine of various individuals as well as two different xiphidiocercariae.3This is believed to be possibly the first record of the occurrence in South Africa of aChaetogasterwhich preys on larval trematode

ISSN:0370-2774    

DOI:10.1111/j.1096-3642.1955.tb00606.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

SUMMARYThe morphological adaptations of the alciopid and lopadorhynchine polychaetes for a pelagic mode of life are compared, with particular reference to the organs concerned with feeding and reproduction. Both groups are predatory, but feed in different ways;Lopadorhynchushas poorly‐developed eyes but long cirri, anterior segments modified for grasping, and large pharyn‐geal glands; alciopids have large eyes and the most advanced have long eversible proboscides. Many alciopids have evolved a copulatory mechanism whereby the sperm are transfered to the female which stores them in receptacula until required. The phylogenetic relationships of the different genera are briefly descri

ISSN:0370-2774    

DOI:10.1111/j.1096-3642.1955.tb00607.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

SUMMARY.1During 1948–1952 a large number of small terrestial mammals were collected in connexion with Scrub‐Typhus investigations.2Simple standard data of weight and state of fertility of these animals were kept, and the results are summarized in table 15.3With a few exceptions, the sex ratio approximated to equality. Of the exceptions, most could be shown to be due to bias in collecting. In a few species particularly associated with man, however, there was an apparent loss of males in the higher weight groups, suggesting a higher death rate among males. In the house mouse,Mus musculus, however, there was an excess of males.4Males showed a distinct annual variation in the fertility and weight of testes. Forest rats showed an increase in fertility during the middle of the year, but the house shrew,Suncus murinus, showed a cycle of reverse phase. The variation did not appear to be great enough to affect breeding.5The mean weight of the males at the onset of fertility was calculated from the regression of percentage‐fertile on body‐weight, with scales suitably adjusted.6Females showed a slight annual variation in pregnancy rate too slight to delimit any breeding seasons. The mean weight at onset of pregnancy was similarly estimated.7The numbers of embryos were recorded and used to calculate a mean embryo number. Combined with the pregnancy rates this gave an estimate of the reproducti

ISSN:0370-2774    

DOI:10.1111/j.1096-3642.1955.tb00608.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY

摘要:

SUMMARY.1. During 1948–1952 a large number of small terrestial mammals were collected in connexion with Scrub‐Typhus investigations.2. Simple standard data of weight and state of fertility of these animals were kept, and the results are summarized in table 15.3. With a few exceptions, the sex ratio approximated to equality. Of the exceptions, most could be shown to be due to bias in collecting. In a few species particularly associated with man, however, there was an apparent loss of males in the higher weight groups, suggesting a higher death rate among males. In the house mouse,Mus musculus, however, there was an excess of males.4. Males showed a distinct annual variation in the fertility and weight of testes. Forest rats showed an increase in fertility during the middle of the year, but the house shrew,Suncus murinus, showed a cycle of reverse phase. The variation did not appear to be great enough to affect breeding.5. The mean weight of the males at the onset of fertility was calculated from the regression of percentage‐fertile on body‐weight, with scales suitably adjusted.6. Females showed a slight annual variation in pregnancy rate too slight to delimit any breeding seasons. The mean weight at onset of pregnancy was similarly estimated.7. The numbers of embryos were recorded and used to calculate a mean embryo number. Combined with the pregnancy rates this gave an estimate of the reproducti

ISSN:0370-2774    

DOI:10.1111/j.1096-3642.1955.tb00609.x

出版商:Blackwell Publishing Ltd    

年代:1955

数据来源: WILEY