GENERAL CONSIDERATIONS 25 



As there are few details in the structure of a simple flagellate on 

 which to focus attention, descriptions of division processes are practically 

 limited to the history of the nucleus, kinetic elements, and the more 

 conspicuous plastids. Here, in the main, are fairly prominent granules 

 of different kinds, which divide as granules, and, save for the chromatin 

 elements of the nucleus, without obvious mechanisms (see MacLennan, 

 infra, Chapter III ) . 



In the simpler cases there is little evidence that can be interpreted to 

 indicate reorganization at the time of division, and that little is con- 

 fined to the motile organs. In the more complex forms, however, there 

 is marked evidence of deep-seated changes going on within the cell. 



The earlier accounts of cell division in the simpler flagellates de- 

 scribed an equal division of all parts of the body, including longitudinal 

 division of the flagellum, if there were but one, or equal distribution 

 if there were more. One by one such accounts have been checked by 

 use of modern methods, until today there remains very little substantial 

 evidence of the division of the flagellum. The basal body and the 

 blepharoplast usually divide, but the flagellum either passes unchanged 

 to one of the daughter cells, as in Crithidia, Trypanosoma, and others, 

 or is resorbed into the cell. In some doubtful cases it may be thrown 

 off. If the old flagellum is retained in uniflagellate forms, the second 

 flagellum develops by outgrowth of the basal body or the blepharoplast. 

 If the old flagellum is resorbed, both halves of the divided kinetic body 

 give rise to flagella by outgrowths. Similarly if there are two or more 

 flagella, one or more may be retained by each daughter cell, while the 

 others, making up the full number, are regenerated. 



Reorganization is indicated, to some extent, by these cases in which 

 the old flagellum is resorbed. It is still better indicated by a number 

 of flagellates in which the cytoplasmic kinetic elements, as well as the 

 flagella, are all resorbed and replaced by new combinations in each of 

 the daughter cells. Thus in Spongomonas splendida, according to Hart- 

 mann and Chagas (1910), the old blepharoplasts and two flagella 

 are resorbed and new ones are derived from centrioles of the nuclear 

 division figure. The phenomenon cannot be regarded as typical of the 

 simple flagellates, for in the great majority the kinetic elements are 

 self-perpetuating, even the axostyles, according to Kofoid and Swezy 

 (1915), dividing in Trichomonas. This, however, requires confirmation. 



