ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1969.tb08447.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

Electron‐microscopy, histology and the preparation of latex corrosion casts were the principal techniques employed. The terminal twigs of the portal and hepatic venous systems inter‐digitate with one another, and are connected by a short network of sinusoids in both central and peripheral regions of the liver. The liver lobule is an elongated unit of hepatic cells with a polygonal cross‐section containing a three‐dimensional lattice of interconnected sinusoids. Lobules are not discrete vascular units as sinusoidal connections join them together. The parenchyma consists of anastomosing sheets of hepatic cells which enclose the sinusoids. Each sheet is two cells thick. Bile canaliculi are formed as intercellular spaces at the apices of three, four or five hepatic cells, and are surrounded by a condensed homogeneous zone of cytoplasm. They do not enclose individual cells (as in the mammal) but course between the two cell layers of the sheet. The electron‐microscopical structure differs from that of the mammal in that the sinusoidal endothelium is fenestrated and partially discontinuous. Intercellular spaces frequently contain white blood cells. A basement membrane underlies the sinusoidal endothelium but it is poorly developed and, in many places, disc

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1969.tb08448.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

Growth in length of the single bones in the cranial base, changes in angulation between these bones and changes in shape of the cranial base have been studied in the rat by serial roentgenocephalometry between 14 and 60 days.All the bones studied showed increase in length during the whole period. However, differences in both absolute and relative increase were found. Sex differences were as a rule of significance from 21 days of age. This phenomenon was explained as a difference in time of maturation between males and females.The cranial base became more dorsally concave with increasing age. This was found to be due to changes in angulation between the basisphenoid bone, the basioccipital bone and the cribriform plate of the ethmoid bone.The development of the rat skull from a clinorhynchal to an orthocranial type was found to be due to a combination of the changes in the cranial base and a high degree of stability of the angle between the cribriform plate and the nasal bone.Furthermore a marked stability of the relative position of the sphenooccipital synchon‐drosis during growth was found. This area corresponds to the position of the hypophysi

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1969.tb08449.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

An earlier study ofDiscocotyle sagittataLeuckart had suggested that the parasite may locate its host by responding to olfactory stimuli emanating from the skin of salmonids but this has now been shown to be untrue. The process of infection involved two stages: first the larvae (oncomiracidia) swim up to the surface waters in response to light and during this phase, they are uninfective; secondly the larvae lose their attraction to light, and if taken in with the respiratory current of a trout at this stage, they stand a good chance of successfully attaching to the gills. The life cycle of the parasite is shown to be synchronized with that of its host.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1969.tb08450.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

Apodemus sylvaticus(L.) is phenotypically and taxonomically uniform over a wide area in Europe, but it has been split into 15 races or subspecies in the Hebridean and Shetland groups of islands. It is argued that with one conceivable exception (A. sylvaticus hirtensisof St Kilda) these could not be pre‐glacial survivors. Furthermore the putative relationships of the different races (as revealed by a study of population samples from 26 localities) make it highly unlikely that the island races are relicts of an early post‐glacial colonization. It is much more probable that they were introduced by man, and the Vikings or their descendants seem the most likely agents.Despite having been isolated only during historical times, many of the races are quite distinct. It is suggested that this is a consequence of chance genetical differences among the founding members of each population (irrespective of any later adaptations), and that this is a method whereby rapid changes in gene frequencies can be achieved, and also provides an example of incipient speciat

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1969.tb08451.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

The Uganda defassa waterbuck is a large African antelope which in western Uganda breeds throughout the year. The adult male averaged 520 lb and the adult female 410 lb in weight. After weaning, at six to eight months, males joined a bachelor herd whilst some females possibly formed spinster groups. The bachelor herd inhabited a home range covering several male territories. At age five to six years a bachelor male attempted to establish his own territory, normally becoming territorial by age seven. A year‐round territory was then maintained throughout life, but at age nine to ten owners were often driven into small, unfavourable areas by younger males. Boundaries were defended by fighting and by typical bovid intimidatory displays. Territories were not actively marked by their owners but owners were apparently identified by odour. Females adopted home ranges covering several male territories, restricting their ranging with increasing age. These home ranges seemed owned by groups of females who moved within them as individuals, associations between particular females being flui

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1969.tb08452.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

The morphology of the head and action of the mouthparts during feeding are described for the primitive brachyceran larva,Rhagio scolopaceus. This is then compared with the larva of the stratiomyid,Sargus bipunctatusScopoli. Both may be found in the same type of habitat, such as dung compost, but whilstRhagiois a carnivore, Sargus is a detritus feeder. The evolution of the mouthparts is discussed and the mode of feeding of these larvae is compared with that of other Brachycera.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1969.tb08453.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY

摘要:

Cyclical changes in the histology of the testis ofTilapia mossambicaare described. The immature virgin testis contains primary germ cells and primary spermatogonia lying within a body of connective tissue. Just before spawning the testis is packed with sperm but cells at all stages of spermatogenesis are also present. After spawning the unexpelled spermatozoa undergo phagocytosis. No quiescent period during spermatogenesis has been observed though there are two periods of increased spermatogenetic activities. The stages of maturation of the testis are also reported. Five stages are distinguished.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1969.tb08454.x

出版商:Blackwell Publishing Ltd    

年代:1969

数据来源: WILEY