This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1878 Excerpt: ...whence they enter into the bodies of their hosts, and in those whose life-history we know, the free and parasitic conditions appear very dissimilar. It has been supposed' and with reason that most of the free Nematelmians found in stagnant pools are early stages of parasitic species. Gordiacece.--The horsehair-like ...
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1878 Excerpt: ...whence they enter into the bodies of their hosts, and in those whose life-history we know, the free and parasitic conditions appear very dissimilar. It has been supposed' and with reason that most of the free Nematelmians found in stagnant pools are early stages of parasitic species. Gordiacece.--The horsehair-like thread-worm which is found in rainwater pools is an example of a second order of round worms. This remarkable animal begins life as a little larva living in mud or in water pools; it is armed with a boring spine, whereby it pierces into the body of a beetle or other aquatic or terrestrial insect; here it becomes encysted, and, having grown in this condition to a considerable length, often ten times as long as its host, it becomes free and aquatic and produces its eggs. So rapidly do some F of these multiply, as, for example, the common Mermis albicans, that they have given rise to the belief that they have fallen as 'worm-rains.' These worms are called Gordiaceae and are distinguished from the other round-worms by the rudimentary condition of their digestive canal. They are also remarkable for their extreme tenacity of life, as they can be dried into hard brittle threads and yet appear lively and active on being moistened. Class IV. Acanthocephala.--The ' thorn-headed' worms are rounded, or cylindrical, each with a protrusible proboscis armed with many recurved hooks. They are remarkable for the total absence of the mouth and intestine in their adult condition. The commonest species are found in the intestines of swine, &c., with their heads buried in the substance of the wall of the digestive tube. CHAPTER XII. NON-PARASITIC WORMS. Class V. Wheel-Animals, Rotatoria.--On tracing the development of the more complex free worms we find that the ...
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