. The biology of the protozoa. Protozoa; Protozoa. MORPHOLOGY AND TAXONOMY OF THE SARCODINA 111 passing through pores in the septa maintain all parts of the soft body as a unit mass. In monothalamous and from the last-formed chamber of polythalamous forms, a large mass of protoplasm gives rise to the pseudopodial network which acts as a trap for the capture of diatoms, Crustacea, rotifers and other smaller objects used as food. In the perforate types pseudo- podia are also, protruded through the finer pores (foramina) of the shell. One large vesicular nucleus is characteristic of both single a
. The biology of the protozoa. Protozoa; Protozoa. MORPHOLOGY AND TAXONOMY OF THE SARCODINA 111 passing through pores in the septa maintain all parts of the soft body as a unit mass. In monothalamous and from the last-formed chamber of polythalamous forms, a large mass of protoplasm gives rise to the pseudopodial network which acts as a trap for the capture of diatoms, Crustacea, rotifers and other smaller objects used as food. In the perforate types pseudo- podia are also, protruded through the finer pores (foramina) of the shell. One large vesicular nucleus is characteristic of both single and many-chambered types. In the latter the nucleus may be confined to the first formed, or inner, cham- bers, although it may wander throughout the entire organism. In many cases it is replaced by several nuclei, and there is a gen- eral tendency throughout the group to form chromidia by multiple division, or fragmenta- tion of the primary nuclei. Reproduction may or may not be accompanied by fertilization phenomena and throughout the group there is a more or less reg- ular alternation of sexual and asexual processes, accompanied in many cases by morphological evidence of sexual or asexual generation. In its simplest ease, asexual reproduction consists of so-called budding division. In Allogromia, for example, the pro- toplasm streams out of the shell mouth and forms a ball of protoplasm of about the same size and shape as the parent organism; on the extruded bud a daughter cell is secreted and after division of the nucleus and migration of one of the daughter nuclei, the bud becomes detached and begins an independent existence. In the polythalamous forms, an initial shell of one chamber contains an organism which grows and buds in a similar manner, but the bud does not become detached. According to the type of budding shell types known as Xodosarian (Fig. 186), Frondicularian and Rotalian, are formed (Fig. 187). A new shell is deposited about the naked bud and thus a second ch
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