Quarterly journal of microscopical science . he purpose of their bcliaviour seems to be to getthe body into as small space as possible, and especially to keep 696 RAYMOND TEARL. the head from drying. At fairly frequent intervals theanimal straightens out and extends the head in front as faras possible, and makes feeling movements. It is thenwithdrawn, and the animal curls up again. After the dryinghas proceeded for some time the most characteristic featureof the whole reaction appears. This is a lengthening of theposterior part of the body to its fullest extent. The posteriorend then attaches
Quarterly journal of microscopical science . he purpose of their bcliaviour seems to be to getthe body into as small space as possible, and especially to keep 696 RAYMOND TEARL. the head from drying. At fairly frequent intervals theanimal straightens out and extends the head in front as faras possible, and makes feeling movements. It is thenwithdrawn, and the animal curls up again. After the dryinghas proceeded for some time the most characteristic featureof the whole reaction appears. This is a lengthening of theposterior part of the body to its fullest extent. The posteriorend then attaches itself to the surface, and strong waves ofcontraction, like those in the crawling movement, pass overthe body from the posterior end forward. No progressivemovement is made, but backward crawling is evidentlyattempted, and is only prevented by the dry surface whichthe animal is on. There may be considerable variation in thefirst part of the reaction with regard to the curling up ; thismay appear or may not, but the attempted backward crawl-. EiG. iJ.—DiHgraiu showing the reaction of Plaiiaria to desiccation. ing movement of the posterior part of the body I have fV)undto be a constant feature in the experiments which I haveperformed. When the dorsal surface of the worm becomesdry all movement ceases. If (piickly })ut back into the waterthe worm will usually recover completely, even though allmovement has ceased in the air. If the worm is put on a slide in the centre of a small areawhich has been wet, but on which there is no standing water,it will squirm about and extend the head frequently, as inthe last experiment. If the head goes outside the wet areait is very quickly jerkid l)ack, and the specimen gives thenegative reaction, i. e. turns away from the side attem])ted backward crawling occurs in this case just asin the otlieis, ji short time l)eb)ie the dorsal surface diies olf. It is to be noted tluit tlien- is never any actual ju-ogressive MOVEMENTS, ETC.,
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Keywords: ., bookcentury1800, bookdecade1850, bookpublisherlondo, bookyear1853
