ISSN:0370-0461    

DOI:10.1111/j.1095-8312.1950.tb00583.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

摘要:

SUMMARY.1Normal locomotion inGeonemertes dendyitakes place by ciliary action. The animal secretes mucus over its whole surface and, though terrestrial, moves by swimming in this mucus, which is left as a trail behind it. The animal is negatively photoklinotactic; the swaying lateral movements of the head responsible for this taxis are muscular. When suddenly stimulated the animal displays an escape reaction by using its proboscis. A simultaneous contraction of all the circular musculature causes its eversion. The animal then flies forward as a wave of longitudinal contraction and circular relaxation spreads up the body and proboscis.2Normal locomotion inRhynchodemus terrestristakes place through muscular waves passing backwards down the ciliated muscular creeping sole of the ventral surface. A continuous mucus trail is left as the animal glides forward. The animal is photoklinotactic. InR. bilineatusthese muscular waves are enormously exaggerated, and only touch the substratum at their lower surface. The animal thus moves by continually producing a succession of ‘myopodia’ which develop in the neck region, protrude down to make contact with the substratum and then pass back along the ventral surface. The animal leaves a succession of isolated mucus foot‐marks. Through the co‐operation of muscular and ciliary action, the body surface continually glides forward where it is incontactwith each foot‐mark. This animal also is negatively photoklinotactic.3R. terrestrison occasion may show large leech‐like locomotor movements due to powerful antiperistaltic waves in the hinder part of the body.R. bilineatushas a specialized muscular cephalic hood. This may on occasion be used as an anterior sucker in leech‐like progression with alternate longitudinal contraction and extension.4The varied ways in which these comparatively simple ciliary and muscular effector systems are utilized for progression are discussed. An animal may develop any convenient property of its effector system to meet the locomotor requirements of its behaviour pattern. At times it may ‘cheat’, as in beetles that swim by local lowering of the surface tension.5The occurrence of a land planarian new to Britain is recorded. It is identified asGeodesmus bilineatusMecznikow–Rhynchodemus bilineatus(Mecznikow). Its resemblance extends to internal structure.6R. bilineatusis congeneric withR. sylvaticusLeidy. Both are generically distinct fromRhynchodemus terrestrisO. F. Müller. The latter should not remain named eitherRhynchodemus terrestrisorGeodesmus terrestrisas it has been by some recent authors. It require

ISSN:0370-0461    

DOI:10.1111/j.1095-8312.1950.tb00584.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

ISSN:0370-0461    

DOI:10.1111/j.1095-8312.1950.tb00585.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

ISSN:0370-0461    

DOI:10.1111/j.1095-8312.1950.tb00586.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

ISSN:0370-0461    

DOI:10.1111/j.1095-8312.1950.tb00587.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

ISSN:0370-0461    

DOI:10.1111/j.1095-8312.1950.tb00588.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

ISSN:0370-0461    

DOI:10.1111/j.1095-8312.1950.tb00589.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

ISSN:0370-0461    

DOI:10.1111/j.1095-8312.1950.tb00590.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

摘要:

SUMMARY.The present note describes six specimens ofScyliorhinus caniculuswhich show sexual abnormalities. Specimen 1 is an hermaphrodite fish where the gonad has presumably undergone change from the male condition. Specimens 2 and 3 show abnormal development of ducts and secondary sex characters appropriate to the opposite sex, together with unilateral inequality of the development of the sexual organs appropriate to the sex of the animal. Degeneration of the gonad and poor duct formation characterize specimens 4 to 6.

ISSN:0370-0461    

DOI:10.1111/j.1095-8312.1950.tb00591.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY

ISSN:0370-0461    

DOI:10.1111/j.1095-8312.1950.tb00592.x

出版商:Blackwell Publishing Ltd    

年代:1950

数据来源: WILEY