334 BIOLOGY OF THE PROTOZOA 



out of the shell Diouth and forms a ball of protoplasm of al)out the 

 same size and shape as the parent organism; on the extruded bud 

 a daughter shell 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 (Fig. 149). In the poly- 

 thalamous forms, an initial shell of one chamber contains an organ- 

 ism 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 Nodosarine, Frondicularian and Rotalian, are formed 

 (Fig. 150). A new shell is deposited about the naked bud and thus 

 a second chamber is added to the first, while the protoplasm by 

 division of the nucleus, without complete cell division, becomes 

 })inucleated or multinucleated. In a similar manner other cham- 

 bers are added to those already formed until complicated aggre- 



B C 



Fiu. 150. — Types of polythalamous Foraminifera shells. A, Nodosarine type; B, 

 frondicularian type; C, spiral type. (From Calkins after Carpenter.) 



gates measuring 3 or more inches in diameter in some cases, result 

 (Nummnliies, etc.). These, however, are to be regarded as single 

 individuals of syncytial nature illustrating growth and differentia- 

 tion rather than reproduction. With the formation of a brood of 

 reproductive bodies each of which produces a similar multinucleated 

 individual we can speak of asexual reproduction in a strict sense. 

 Thus in FolystomcUa crispa (Fig. 119, p. 239), after multiplication 

 of the nuclei, the latter give rise by fragmentation to a large number 

 of minute nuclei having the significance of chromidia. The plasm 

 forms islands about each of these minute nuclei, or groups of them, 

 and is then broken up into as many minute cells as there are islands. 

 These small cells, in the form of amo'lnihe or amcx^bospores leave 

 the parent shell by way of the foramina or l)y the mouth opening of 

 the last chamber and after a short period of amoeboid movement 

 settle down and secrete the characteristic shell chamber. This 



