. ProtozooÌlogy. Protozoa; Protozoa, Pathogenic. 96 PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA chromidia form, gives rise to numerous buds, each of which is pro- vided with chromidia, but with no part of the vegetative nucleus. Such buds uhimately form the conjugating gametes in forms Kke arcella, difHugia, centropyxis, etc. In parasitic forms hke Entavieba histolytica, the cause of tropical dysentery, or Neurorydes hydrophobia, the cause of rabies, there is a similar bud formation, the buds having the characteristic chromidia; their further fate, however, is unknown, the sexual processes of the
. ProtozooÌlogy. Protozoa; Protozoa, Pathogenic. 96 PHYSIOLOGICAL ACTIVITIES OF THE PROTOZOA chromidia form, gives rise to numerous buds, each of which is pro- vided with chromidia, but with no part of the vegetative nucleus. Such buds uhimately form the conjugating gametes in forms Kke arcella, difHugia, centropyxis, etc. In parasitic forms hke Entavieba histolytica, the cause of tropical dysentery, or Neurorydes hydrophobia, the cause of rabies, there is a similar bud formation, the buds having the characteristic chromidia; their further fate, however, is unknown, the sexual processes of these organisms not having been made out (see p. 303). A much more highly evolved method of division is found in some of the colony forms of protozoa, where, as in Gonium â pectorale (Fig. 35), for example, each of the sixteen cells of the parent colony forms simultaneously a daughter colony of sixteen cells. Here Fig. 34. Endogenous budding in Suctoria. (After Biitschli.) A, B, two stages in the formation of the bud in Tokophrya quadripartita, CI. and Lach.; c, the bud liberated as a "swarmer;" C, buds (e) in Acineta tuberosa, Elir.; d, a bud liberated. simple division is followed by association of the daughter cells, and individuals result which have passed through an actual, although primitive, ontogeny. In spore formation, finally, we find one of the most prolific methods of reproduction known. Here the organism breaks down simultane- ously into great numbers of daughter elements, each dissimilar to the parent in size if not in other characters. This process, involving as it does the cessation of normal vegetative life with its ordinary processes of digestion, assimilation, etc., usually takes place under the protection of an outer covering or cyst, such encystment being a common phe- nomenon among the protozoa, an outer covering of gelatinous material l^eing thrown out on the surface of the organism whenever the condi- tions of the environment become unsuitable. T
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