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ECTOSPORA

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Originally appearing in Volume V08, Page 910 of the 1911 Encyclopedia Britannica.
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ECTOSPORA , a homogeneous and natural See also:

division of Protozoan parasites included under the See also:Sporozoa; they comprise the three orders, See also:Gregarines, See also:Coccidia and See also:Haemosporidia. The defining See also:character of the Ectospora is that the spore-See also:mother-cells (sporoblasts) are formed at the periphery of the See also:parent-individual (sporont); we may, however, go further, and say that the formation of all the different reproductive elements is uniformly peripheral or exogenous. Two other very See also:general features are (a) that the individual trophozoite is uninuclear, and (b) that growth and trophic activity are finished before the multiplicative or reproductive phase sets in. There is now little doubt that the Ectospora possess a flagellate ancestry. The See also:principal facts in favour of this view are as follows: the actual ontogenetic connexion known to exist between certain Haemoflagellates and certain Haemosporidia (see See also:TRYPANOSOMES); the See also:possession by many Coccidia of biflagellar microgametes (male elements), whose general structure greatly resembles that of a Heteromastigine Flagellate; the possession by various parasitic Flagellates (e.g. Her petomonas) of an attached, resting phase, when the parasites become gregariniform, which strongly suggests the attached phase of many See also:young, growing Gregarines; the typical gregarinoid and euglenoid movements of Gregarines and of the germs or other stages of Coccidia and Haemosporidia, which are quite comparable with the contractile and metabolic movements of Flagellates; and, lastly, the exogenous type of See also:reproduction, which is easily derivable from the multiple division of certain Haemoflagellates, and this, in turn, from the typical binary See also:longitudinal fission of a Flagellate.

End of Article: ECTOSPORA

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