Elementary text-book of zoology, tr Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote elementarytextbo01clau Year: 1892-1893 PROTOZOA. transverse fission, and also by spore formation in an encysted condition; the latter method seenis in many forms to be preceded by conju- gation. The best known species are Cercomonas Duj. and Trichomonas Donne, of which the first is characterised by the possession of a caudal filament, while Trichomonas has an undulating row of cilia close to the flagella, which are usually two in number (fig. 133). They liv
Elementary text-book of zoology, tr Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote elementarytextbo01clau Year: 1892-1893 PROTOZOA. transverse fission, and also by spore formation in an encysted condition; the latter method seenis in many forms to be preceded by conju- gation. The best known species are Cercomonas Duj. and Trichomonas Donne, of which the first is characterised by the possession of a caudal filament, while Trichomonas has an undulating row of cilia close to the flagella, which are usually two in number (fig. 133). They live principally in the intestines of 'Vertebrates, but are also found in Invertebrates. Cercomonas intestincdis Lauibl. and TricJwinonas vaginalis Donne, are found in Man. The Monads,* which cannot be sharply separated from the Jfonadina-, are simple cells free from chlorophyll, the swarm spores of which usually pass into an amoeboid stage, and after receiving nourish- ment enter upon a motionless stage characterised by the possession of a firm cell-membrane. A number of them (Monas, Pseudospora, ColpodeUa), the so-called Zoospores, are mastigopods resembling the niastigopods (swarm spores) of Myxo- mycetes, and, with the exception of Colpoddla, grow up to creeping Amoeba? which protrude pointed pseudopodia. In this stage they may also be simply regarded as small plasmodia, especially when, as in Fionas amyli, several masti- FIG. 133.— a, Cermmonat intesHnuii*. gopods fuse together to form the amoeba. LeucktrtT'0' ^''^ (Bfter R' The>' tlien take— in Colpodetta without first entering the amoeba stage — a globu- lar form, their surface develops a membrane, and in this cyst they break up by division of protoplasm into a number of segments which pass out as swarm spores and repeat the course of development (Colpodetta pugndx to Chlamydomonas, Pseudospora volrocis). Other Monads, the so-called Tetraplasta (Vampyrdla, Xuclearia], do not puss through the mastigopod (swarm spore
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