An Introduction to Nematology, Vol. 2 (Classic Reprint) - Hardcover

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Excerpt from An Introduction to Nematology<br/><br/>Some nematodes have both free-living and parasitic stages, the free-living stages being larvae, the parasitic stages late larvae and adults. In these we find young larval stages (the first and second) feeding upon bacteria and similar organic matter, the third stage usually ensheathed or persistent, this commonly being the infective stage. Upon entering the host these species develop through the fourth stage to the sexually mature adult. A further development of parasitism is indicated by the ah sence of the free-living stages. Eggs of the parasite pass out of the host and, outside, undergo only embryonic development within the egg shell. In such instances the egg shell is often covered by a protein layer (p. And the embryo often con tains more yolk than forms in which the eggs hatch before en tering the host. With such a completely parasitic mode of existence, the factor of dissemination again becomes manifest and we find still other modifications in the life cycle.

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