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 chamber is added to the first, while the protoplasm by 



Fig. 186. — Diagram to show the 

 mode of origin of the Nodosarine type 

 of Foraminifera shell. 



