. An introduction to zoology : for the use of high schools . hat, twolateral cceca. The water-vascular systemconsists of two convoluted tubes openinganteriorly into the ccelom and posteriorlyinto a contractile bladder, which communi-cates with the rectum. Instead of the elong-ated nerve-cord of the higher Annelids, thereis here only a single ganglion situated abovethe oesophagus, whence are distributed nerve-fibres to the various parts, including the eyesand tactile organs. There are no blood-vessels, and no respiratory organs. The Rotifers hke the Tardigradeshave considerable power of resisti
. An introduction to zoology : for the use of high schools . hat, twolateral cceca. The water-vascular systemconsists of two convoluted tubes openinganteriorly into the ccelom and posteriorlyinto a contractile bladder, which communi-cates with the rectum. Instead of the elong-ated nerve-cord of the higher Annelids, thereis here only a single ganglion situated abovethe oesophagus, whence are distributed nerve-fibres to the various parts, including the eyesand tactile organs. There are no blood-vessels, and no respiratory organs. The Rotifers hke the Tardigradeshave considerable power of resisting death by desiccation, 9. The names of the remaining Classes, which include for themost part parasitic worms, are taken from the form of the body,which is cylindrical in the Nematelminthes but flattened in thePlathelminthes. According to the grade of parasitism, the in-testinal system is more or less reduced, being absent in thosemost completely adapted for a parasitic mode of life. Organs offixation suited to the nature and degree of the parasitism, are. Fig. 150.—Female of Roti-fer. {Ilydatina senta). 224 HIGH SCHOOL ZOOLOGY. also to be recognised. The development is often complicatedby a metamoiphosis, and the creatures often pass through dif-ferent stages of their parasitic life in diiferent hosts, a phenom-enon known as hetercecism.
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1889
