摘要:

SUMMARY1The age of Llyn Tegid trout can be reliably determined from the scales byby counting the number of completed winter bands. The winter rings are formed annually in September‐October.2The seasonal growth pattern of lake trout has been investigated by examination of the scale structure each month and by following the monthly changes in the mean lenghts of each year‐class. Growth is confined to the period February‐March to September‐October, no growth taking place during the winter.3Annual growth has been studied by determining the mean length of trout at the beginning of each year of life. The mean specific growth rate in the lake and streams declines with age and its negative acceleration decreases with age. Growth in Llyn Tegid and the neighbouring streams has been compared with growth in other British waters.4Growth in the tributary streams is better than in the moorland streams but poorer than in the lake. Trout show an increase in growth rate when they migrate from the tributary streams to the lake.5The length‐weight relationship is the same for trout of all ages and in all the localities studied.6Seasonal changes in the usual condition factor, K= weight 104/length3have been determined. K is correlated with the amount of reserve fat stored around the stomach and pylo

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1960.tb05915.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

摘要:

SUMMARY1Observations and experiments on the association betweenCalliactis parasiticaandEupagurus bernhardushave been carried out.2The attachment of the anemone to the shell is achieved by a remarkable manoeuvre involving the attachment of the tentacles and oral disc, the freeing of the pedal disc and its adhesion to the shell by a somersaulting movement, with the eventual release of the oral attachment and the assumption of the normal posture on the shell.3Active participation ofE. bernhardusin detaching the anemone and transplanting it on the shell was not observed, in contrast to the active parts played by the crabsPagurus striatusandP. arrosorin their associations withC. parasitica.4C. parasiticabecomes attacvhed to empty shells no less quickly or frequently than to shells occupied byE. bernhardus.5The anemone readily settles on shells of livingBuccinum undatumin the laboratory and does not desert these for shells occupied by crabs. It does not settle on shells cleaned by boiling in strong alkali.6The respective roles of anemone and crab in the associations betweenCalliactisand these three species of pagurid crabs are discussed from the stand‐points of comparative behaviour and with special reference to the capacities of the actinian neuromuscular system here displaye

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1960.tb05916.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

摘要:

SUMMARYAn account is given of what is known of the habits and life history ofPoecilogale albinuchadrawn from published records supplemented by observations of a tame female formerly in the writer's possession.

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1960.tb05917.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1960.tb05918.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

摘要:

SUMMARYEleven species ofBugulaare known to occur in British waters, including three that have not previously been described. The characters of greatest value for separating these species are reviewed. Full descriptions are given ofB. neritina, B. plumosa, B. purpurotincta, B. stoloniferasp. nov.,B. avicularia, B. turbinata, B. flabellata, B. fulvasp. nov.,B. calathus, B. aquilirostrissp. nov. andB. simplex.The account includes notes on habitat, breeding season and geographical distribution; and a key is provided to facilitate identification.B. ditrupae, from Madeira, is redescribed and compared withB. fulvaandB. aquilirostris, as the three species have hitherto been confused. Synonomies of each are given.TheB. simplexof most authors is not that of Hincks, but another species: possibly of form konwn asB. plumosavar.aperta. B. simplexis theB. flabellataof most American authors, and theB. sabatieriof those writing on Mediterranean Polyzoa. Synonomies ofB. simplexandB. flabellataare given.A full description ofB. turritaand summary descriptions ofB. californica, B. pedataandB. geermanaeare given, and these species are compared withB. stolonifera.The characters ofB. spicataare mentioned as it also has been confused with some of the above species.

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1960.tb05919.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1960.tb05920.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

摘要:

SUMMARY1The following structural modifications ofPeriophthalmus koelreuteri(Gobiidae) are of particular important in locomotion on land.(a) A strenghtening of the pectoral girdle by increased ossificationm, and an enlargement of the areas for muscle attachment. The postaxial rays of the fin are stiffened considerably, and are of the semi‐spinous type. No fusion of the radial elements occures in this species.(b) The relative extension and depression of the pectoral fin axis is greater forP. koelreuterithan other species. This enables the postaxial rays to be swung in almost a vertical plane. The pectoral fin rays are not spread in this species when moving on land, but are bundled together to form a strut.(c) In addition to adducting the basal lobe, theM. coraco‐radialistakes on the new role of maintaining the stability of the shoulder joint, and supporting the body weight.(d) The pelvic bones articulate with the cleithrum, and act as compression structs transmitting the body weight to the pelvic fins. TheM. protractor pelvisand the anterior hypaxial musculature play an important part in supporting the body, and in providing the vertical component of the forces used in skipping. The pelvic fin rays are short and stiff. The first is spinous and the remainder semi‐spinous. The pelvic fins are modified for support, and have lost their suctorial ability.(e) The caudal fin is truncated ventrally. The shor stiff ventral rays are used to anchor the tail during the skip, and to support the hind end of the body when moving on land.2Six modes of locomotion are defined and analysed.(a) Fast swimmingis effected by the tail without the assistance of the paired fins.(b) Paddlingis a slow mode of swimming in which the pectoral fins are used as paddles. Air in the bucco‐pharynx causes the fish to swim with the head partly out of the water.(c) Crutchingis a slow halting motion on land in which the fish is hitched forward on the pectoral fins. The trunk and tail remain stiff, and do not make any sinuous movements. The caudal fin acts as a skid to support the hind end fo the body off the ground. A bilateral synchronization of the paired fins is necessitated by the instability of a three point supporting system. Motion is discontinuous, i.e., it comes to a momentary halt at the end of each locomotory cycle. Analysis of motion films has given conclusive evidence that the pelvic fins contribute to the propulsive thrust, but their contribution is very small. A speed of about 10 cm/sec. is achieved by adult fish (c.14 cm. body lenght).(d) Inskippingthe fish is projected through the air by a propulsive force developed in the axial muscles of the tail. A vertical component is producted by theM. protractor pelvisand the hypaxial muscles. The caudal fin acts as a fulcrum for the skip.(e) Climbing.The ability ofP. koelreuterito climb is limited, due to the fact that the pelvic fins have been modified for a locomotory, rather than a suctorial, function.(f) Skimmingis an activity in which the fish makes a series of bounds over the water. The movements of the tail. A speed of about 2.5 metres/sec. is achieved. Skimming is an escape reaction.3The adaptations shown byPeriophthalmusand tetrapods to terrestrial progression are constrasted, and its bearing on the evolution of the two groups from a

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1960.tb05921.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

摘要:

SUMMARYThe breeding ofArenicola marinafrom two beaches in the Isle of Man, one exposed to and the other sheltered from wave action, was studied. Both populations spawned only once during the year, in autumn, after an extended period of sexual development. The population living in exposed conditions had a higher proportion of juvenile non‐breeding worms than the sheltered populations, due to loss of adult worms (by mortality and/or migration) resulting from unstable environmental conditions. Lugworms from the Isle of Man are capable of becoming sexually mature for the first time in their second year of life and at a size of between 0.5 c.c. and 0.9 c.c. (about 2 to 3 cms. chaetigerous length).Male spawning in 1950 and 1951, detected by the occurrence of sperm puddles on the surface of the sand, occurred mainly during three days at the later November neap tides, but some slight spawning also took place before and after. Female spawning could only be detected by examination of the coelomic contents and it appeared that during both years the male and female spawning was not simultaneous, there being a few days difference in the start and finish of the process.In 1951 spawning occurred in nine populations of British lugworms during the neap tides of October, November and December. In all nine populations the male spawning coincided with one of these neap tides, but at St Andrews worms from below low water neaps spawned during spring tides. In four populations the female worms apparently began or finished spawning slightly earlier than the males. In five populations, spawning was epidemic but in two it extended over a period of several weeks.Possible factors inducing spawning are discusse

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1960.tb05922.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1960.tb05923.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY

ISSN:0370-2774    

DOI:10.1111/j.1469-7998.1960.tb05924.x

出版商:Blackwell Publishing Ltd    

年代:1960

数据来源: WILEY