摘要:

The spinnerets of spiders are carried on the fourth and fifth segments of the abdomen (opisthosoma). Primitively there are two pairs, anterior lateral (al) and anterior median (am) on the fourth segment, and two pairs, posterior lateral (pl) and posterior median (pm) on the fifth,amare present inLiphistiusbut are never functional. In mygalomorphsamare invariably absent, and usuallyalalso. In araneomorphsamare either reduced to a function‐less colulus, perhaps absent altogether, or represented by the cribellum, which is a specialized spinning organ.It seems unlikely that the lateral and median spinnerets correspond to the exopodites and endopodites of a biramous limb, which limbs are characteristic of the Crustacea, a group having no close relationship to the Arachnida. From embryology it seems clear that the lateral spinnerets are the segmental appendages. Glands, here described as the epiandrous glands, very similar to spinning glands, occur on the second abdominal segment of most male spiders. It is suggested that these may be serially homologous with the median spinnerets, which would then not be appendicular in origin but would be modifications of ventral glandular structure

ISSN:0368-2935    

DOI:10.1111/j.1096-3642.1967.tb00504.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

The fishes of the Order Crossopterygii are characterized by a unique articulation within the braincase, by which the anterior division of the endocranium may be moved dorso‐ventrally with respect to the posterior division. The structure of the skull in both groups of crossoptery‐gian fishes (the fossil Rhipidistia and the fossil and Recent Coelacanthini) is such that ‘normal’ operation of the intracranial mechanism involves lateral movements of the cheek region and palate corresponding to the dorso‐ventral movements of the ethmoid portion of the braincase. The hyomandibular has a function of prime importance in integrating the movements of the various skull components relative to each other. There are important differences between the characteristic intracranial mechanisms of Rhipidistia and Coelacanthini which may be interpreted in adaptive as well as morphological terms. Analysis of the intracranial kinetics of the Rhipidistia reveals a trend, in certain lines, for the amount of relative movement between the skull components to be decreased and this may be used to explain the loss of the intracranial joint in the Amphibia during their evolution from the Rhipidistia. The functional significance of the intracranial articulation has both a kinetic and a dynamic aspect and while in the Amphibia the kinetic ability of the skull is almost wholly restricted, the dynamic features of the ancestral condition are modified and developed as the basal articulation between the palate and endocranium is

ISSN:0368-2935    

DOI:10.1111/j.1096-3642.1967.tb00505.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

In the course of a survey of the history of the study of Heliconiinae, particularly their biology, in the eighteenth and nineteenth centuries it is shown thatHeliconius nigromarginatus(Goeze) andH. pallescens(Goeze) arenomina oblita, and thatH. cinereofuscus(Goeze) is not, as always supposed, a species in its own right. A new name is proposed forH. melpomene cybele(Cramer). The origin and application of some of Linnaeus' names is discussed.Illustrations ofHeliconiusby Seba, Clerck, Petiver and Cramer show that three species,melpomene, eratoanddorishave been polymorphic at least since the middle of the eighteenth century.The Indo‐Australian genusCethosiashould probably be included in the Heliconiina

ISSN:0368-2935    

DOI:10.1111/j.1096-3642.1967.tb00507.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Summary.The pangolin scale is a horny derivative of the epidermis. It is complex in structure and is divisible into three distinct regions. The dorsal plate forms approximately one‐sixth of the scale thickness. It is composed of flattened solid keratinized cells without basophilic nuclear remnants. This region tends to fray easily. The dorsal plate contains bound phospholipids and sulphydryl groups but is weak in disulphide bonds.The bulk of the scale is made up of the intermediate plate formed of less flattened cells without basophilic nuclei. This region is rich in disulphide bonds but contains no appreciable bound phospholipids or sulphydryl groups.The ventral plate is only a few cells thick and is rich in bound phospholipids, which also occur in the underlying scale bed epidermis.These three regions of the scale are formed from separate epidermal germinal areas which do not develop a granular layer. Keratohyalin granules are, however, formed in the epidermis between the scales.It is suggested on the basis of histological structure and dishribution of chemical constituents that pangolin scales are probably homologous with primate nails.Evidence against the views that they are homologous with reptilian scales or are derived from compressed hairs is presente

ISSN:0368-2935    

DOI:10.1111/j.1096-3642.1967.tb00508.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Summary.This paper deals with the relationships of two Jamaican crabs with their sacculinid parasites;Geograpsus lividus(Milne‐Edwards) infected bySacculina hartnolliBoschma, andMicrophrys bicornutus(Latreille) infected bySacculina bicuspidataBoschma. The following are the more important features discussed.1The level of infection and the incidence of multiple parasitism.2The modification of the host by the parasite.3The causes of this modification.A number of conclusions were reached.1In these two saceulinids multiple parasitism is due mainly to the invasion of the host by several larvae. In some other saceulinids, however, polyembryony is the principal cause.2The observed host modifications are similar to those described in previous investigations. They tend to change both male and female hosts into ovigerous females, both as regards morphology and behaviour.3The parasite affects its host by interfering with the endocrine system.4The modification of the host is of advantage to the parasite. This could explain why the sacculinid has evolved the power to induce these modification

ISSN:0368-2935    

DOI:10.1111/j.1096-3642.1967.tb00509.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Rates of tail regeneration in the Madeira wall lizard (Lacerta dugesii) and the slow‐worm (Anguis fragilis) were studied.L. dugesiiregenerates very rapidly, the new tail sometimes attaining a maximum rate of growth of 2'6 mm a day during the fifth week after autotomy. By the twelfth week 90% of the original tail length has been replaced. Average regeneration rates of samples of lizards were reduced after repeated autotomies, but our investigation of this problem was probably complicated by another factor, the amount of tail lost, and is inconclusive.The tip of the regenerate grows more rapidly than the rest; no elongation occurs at its cranial aspect.Anguis, even when kept at 27°C, regenerates its tail very slowly, the best performance observed being a new tail of 5 mm after 14 weeks. The longest natural regenerate seen (16 mm) may have taken several years to produce in the wild.The histological features of regeneration inAnguisare basically similar to those in other lizards. The new osteoderms are formed entirely in the subepidermal tissues but have a regular relationship with the scales. Some nerve fibres are regenerated with the ependymal tube.The scales on the lizard's regenerating tail develop in a different manner from those in the lizard embryo and show suggestive resemblances to mammalian hai

ISSN:0368-2935    

DOI:10.1111/j.1096-3642.1967.tb00510.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY