REPROD UCTION 49 



Cytoplasmic Division 



Binary fission. As in metazoan cells, binary fission occurs 

 very widely among the Protozoa. It is the division of the body 

 into two nearly equal daughter cells. In the Amoebaea the body 

 divides simply into two daughter individuals. In Testacea, as a 

 rule, one of the daughter individuals occupies the old test, while 

 the other moves out and forms a new one, as in Arcella and 

 Euglypha. However, in some forms, such as Cochliopodium and 

 Pseudodifflugia, the division is longitudinal, the test dividing 

 also into two parts. 



In the majority of the Mastigophora, the division is longi- 

 tudinal (Fig. 21). The nucleus and the blepharoplast divide 

 first. The old flagellum may or may not be absorbed during the 

 division. The new flagellum or flagella develop from the 

 blepharoplasts. In a few forms, such as Oxyrrhis marina and 

 Lophomonas striata, the cytoplasmic division is transverse. 

 In the latter species the second daughter individual develops its 

 anterior end directed posteriorly. The two almost completely 

 divided daughter individuals may remain together for some 

 time, being connected by a filamentous strand. 



In the Ciliophora the division is usually transverse (Fig. 16). 

 The macro- and micro-nucleus each divide into two, and then 

 the cytoplasmic organelles, such as the cytostome, contractile 

 vacuoles, etc., are regenerated before the body divides into two. 

 Incomplete division of the stalk results in producing arboroid 

 colonies in many Peritrichida. 



Budding. Multiplication by budding, which is less fre- 

 quently found in Protozoa than binary fission, is the formation of 

 one or more smaller individuals from the large parent organism. 

 It is either endogenous or exogenous, depending upon the loca- 

 tion of the developing bud. Exogenous budding is noted in Noc- 

 tiluca (Fig. 35), Myxosporidia (Fig. 23), Telosporidia, Suctoria 

 (Fig. 18), etc. Endogenous budding is found in certain Suctoria 

 (Fig. 173), although it does not seem to occur either in the 

 Ciliata or in the Mastigophora. In Testacea such as Arcella, 

 endogenous budding is said to take place. It occurs quite 

 commonly in numerous members of the Sporozoa. 



Multiple division. In multiple division the body divides into 

 a number of daughter individuals completely, with or without 



