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| View Larger Image | Nematode worms | Paperbackby George Edward Stone (Author)
| List Price: | $20.00 | | | Available: | Usually ships in 24 hours |
| | Binding: | Paperback | | Publisher: | General Books LLC | | Page Count: | 60 Pages | | Publication Date: | August 10, 2009 | | Sales Rank: | 4,914,468th |
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EDITORIAL REVIEWS |
Product Description
Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: Besides the digestive, sexual, and excretory systems, nematodes also have a sort of nervous system, consisting principally of a so called nerve ring, which surrounds the oesophagus just behind its median bulb. This, however, is usually very indistinct and not highly developed. A circulatory system is entirely wanting in nematodes. Description of the Parasitic, Gall Forming Nematode, Heterodera radicola. (a) EARLY .LIFE. Turning now from this typical species of a nematode in its simplest form, to the gall forming species which causes the injury to plants, we shall find some similarities in structure and development and also some striking differences. The egg (Pl. IV., figs. 1-16), as in the other species is an elliptical or rather bean shaped body .1mm. (ftt of an inch) in length, composed of a chitinous membrane inclosing a mass of granular protoplasm and fat globules. The covering, although very thin, is extremely tough and very resistant to heat, cold, chemical substances, etc., affording to the egg contents a protection which is well nigh absolute against the ordinary influences of nature. In its earliest stage the mature egg consists inside the membrane of a loose, undivided mass with a nucleus in the centre. After fertilization the nucleus divides and two cells are formed (Fig. 3). These divide again and again passing through various embryological changes and developing into a young worm as shown at fig. 16. The worm moves about freely in the shell and finally ruptures it and escapes. In its earliest life it resembles the free living species having a similar form and structure. It is a minute worm-shaped creature about .33mm. (7 of an inch) in length, quite invisible to the naked eye. Plate VII., figs. 5 and 6, are intended to give an idea of the size of the wo... |
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