摘要:

Summary.1Traps were set for the field mouse, Apodemus sylvaticus, in a great variety of environments on South Haven Peninsula in Dorset, an area already surveyed by ecologists.2A description is given of the areas chosen for trapping and the trap sites are shown on a map.3The numbers of mice caught in over 50 different environments are given in Table I.4Reasons why these numbers are not comparable are discussed.5Comparisons are nevertheless attempted between woods, dunes and heaths, and the woods are shown to have been the most populous.6Outside the woods the largest numbers of mice recorded in Table I were caught where the traps were set in a long line; this was probably because a line of traps drains a larger area than a cluster where other conditions are equal.7The same individuals were caught in several different environments.8In considering the preference of mice for different environments a method of census is needed which will discriminate between residents, visitors and mere passengers. The difficulty of finding such a method is emphasized.9A list is given in Table III of the distances between any two traps visited by the same mouse. Only one distance of over 400 yards is recorded, two between 350 and 400 yards, while below 250 yards the records become very frequent.10These distances do not show the length which a mouse can travel but result from the position of its nest relative to our arbitrarily chosen trapping sites. The longest distances are likely to have been recorded when the nest was centred between two sites.11The number of mice common to two areas depends not only on the distance between the areas but also on whether the intervening ground is habitable. Uninhabitable areas such as swamps are not so much barriers to mice as ground from which there are no mice wandering out in each direction.12Mice released at a distance from where they were caught found their way back over much greater distances than those recorded here for natural wandering. Longer wanderings observed elsewhere suggest that the mice may have been familiar with the country through which they returned, but this is hard to believe in the case of returns of over 600 yards from the opposite side of the lake.

ISSN:0368-2935    

DOI:10.1111/j.1096-3642.1951.tb01850.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

Summary.The possible significance of the developmental features of Leiopelma and Ascaphus is best considered in relationship to their systematic position amongst frogs. Nobls'e (1931) recognition of the primitiveness of these two genera has been upheld and confirmed by subsequent investigators. For example:—1There are 9 presacral vertebrae in Leiopelma and Ascaphus, but not more than 8 in any other living frogs.2Leiopelma and Ascaphus agree with primitive urodeles in that the interdorsals and interventrals remain cartilaginous throughout life. The vertebrae are thus amphicoelous, but this condition is not found in any other living Anura.3In the Anura, the reduction of true ribs has reached an extreme. Only Leiopelma, Ascaphus and the Discoglossid frogs retain ribs in the adult, though Pipids have ribs while larvae (Noble, 1931). In the adult Leiopelma, there are at least two pairs of true ribs, and sometimes indications of a third pair are visible.4Abdominal ribs were well developed in the extinct Branchiosaurs. Such ribs appear in the myosepta of the M. rectus abdominis of Leiopelma, and traces occur in Bombina (Goette). Similar pieces of cartilage have been described in Necturus, but, according to Noble, in no urodele are they as well developed as in Leiopelma.5Leiopelma and Ascaphus are more primitive than other Anura in that the adult retains two tail‐wagging musclea, the pyriformis and caudali‐pubo‐ischiotibialis, although the tail has disappeared. (Noble, 1931.)6Posterior cardinal veins are present in the larvae of frogs and urodeles. In the adult Leiopelma, Ascaphus and Bombina, as well as in some adult urodeles, both posterior cardinal veins and the posterior vena cava occur together. The posterior cardinal veins of the adult Leiopelma are very well developed.The above are some of the more important primitive characters of Leiopelma and Ascaphus and in many of them the two frogs show a close relationship to urodeles. Furthermore, many morphological characters previously considered to separate the Urodela from the Anura are now found not to apply to these primitive genera. Their anatomical relationships lend no support to the opinions advanced by Wintrebert (1922), Holmgren (1933, 1939), Säve‐Söderbergh (1934, 1936) and Herre (1935) and recently upheld by Jarvik (1942) that Urodeles and Anurans have arisen independently of each other. For example, differences in the connections between the quadrate and the neurocranium in Urodela and in Anura seemed to demonstrate a gap which is now bridged by Ascaphus (Pusey, 1938, 1943) and by Leiopelma. The separation of the nasal capsules and the presence of an ethmoidal region of the cranial cavity in Leiopelma provides a condition intermediate between the two orders. The course of the hyoman‐dibular nerve in Leiopelma displays relationships more comparable to those pertaining to Urodela than to Anura.But it is not only in many details of its adult anatomy that Leiopelma resembles urodeles; there are also striking resemblances in its development. The similarity is well shown by summarizing the developmental features and comparing them with those of urodeles laying large yolky eggs that undergo lengthy intracapsular development either in wat

ISSN:0368-2935    

DOI:10.1111/j.1096-3642.1951.tb01851.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

摘要:

Summary.It has been shown by rearing and breeding experiments that the amphipod Jaesa falcata (Montagu 1808) is a polymorphic species.The species falls into two main classes or divisions, characterized particularly by the differing setation and shape of the aecond antennae, and the second gnathopods of the males. These divisions are called here, in accordance with their appearance, the Broad end the Narrow Forms. There is a third Form, in which the antennal oharacters of both the other Forms ere combined with either the Broad gnathopod or the Narrow one.In addition a number of Minor variants occur within the limits of the two main divisions.The species also shows male intersexuality.The trivial names enumerated below we consider synonyms of Jassa falcata (Montagu). It is not necessary to give the full synonymy list here as that is included in the following review of the bibliography.

ISSN:0368-2935    

DOI:10.1111/j.1096-3642.1951.tb01852.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY

ISSN:0368-2935    

DOI:10.1111/j.1096-3642.1951.tb01850a.x

出版商:Blackwell Publishing Ltd    

年代:1951

数据来源: WILEY