REPRODUCTION 145 



plasmic masses of the parent body. In this process the nucleus 

 may undergo either simultaneous multiple division, as in Aggregata, 

 or more commonly, repeated binary fission, as in Plasmodium (Fig. 

 225) to produce large numbers of nuclei, each of which becomes the 

 center of a new individual. The number of daughter individuals often 

 varies, not only among the different species, but also within one and 

 the same species. Multiple division occurs commonly in the Fora- 

 minifera (Fig. 184); the Radiolaria (Fig. 194), and various groups of 

 Sporozoa in which the trophozoite multiplies abundantly by this 

 method. 



Budding. Multiplication by budding which occurs in the Proto- 

 zoa is the formation of one or more smaller individuals from the 

 parent organism. It is either exogenous or endogenous, depending 

 upon the location of the developing buds or gemmules. Exogenous 

 budding has been reported in Acanthocystis, Noctiluca (Fig. 107), 

 Myxosporidia (Fig. 68, h), astomatous ciliates (Fig. 266), Chono- 

 tricha, Suctoria (Fig. 331, k), etc. Endogenous budding has been 

 found in Testacea, Gregarinida, Myxosporidia (Figs. 247, e; 249, j), 

 and other Sporozoa as well as Suctoria (Fig. 331, A). Collin observed 

 a unique budding in Tokophrya cyclopum in which the entire body, 

 excepting the stalk and pellicle, transforms itself into a yoUng 

 ciliated bud which leaves sooner or later the parent pellicle as a 

 swarmer. 



Plasmotomy. Occasionally the multinucleate body of a protozoan 

 divides into two or more small, mutinucleate individuals, the cyto- 

 somic division taking place independently of nuclear division. This 

 has been called plasmotomy by Doflein. It has been observed in the 

 trophoxoites of several coelozoic myxosporidians, such as Chloro- 

 myxum leydigi (Fig. 68), Sphaeromyxa halbianii (Fig. 68), etc. It 

 occurs further in Mycetozoa (Fig. 156), Protociliata and certain 

 Sarcodina (Pelomyxa). 



Colony formation 



When the division is repeated without a complete separation of 

 the daughter individuals, a colonial form is produced. The compon- 

 ent individuals of a colony may either have protoplasmic connections 

 among them or be grouped within a gelatinous envelope if completely 

 separated. Or, in the case of loricate or stalked forms, these exo- 

 skeletal structures may become attached to one another. Although 

 varied in appearance, the arrangement and relationship of the com- 

 ponent individuals are constant, and this makes the basis for dis- 

 tinguishing the types of protozoan colonies, as follows: 



