REPRODUCTION 



237 



membranes as is the case in numerous Dinoflagellida, in CJiloro- 

 gonium eiichlorum (Fig. 117), Phacotiis lenticular ius, etc. In animal 

 flagellates, however, particularly the parasitic forms, a highly char- 

 acteristic method of multiple division is widely distributed. Here in 

 certain phases or under conditions not yet well understood, trypano- 

 somes, trichomonads, lophomonads and other parasitic flagellates 

 undergo a process of asexual sporulation to which the specific term 

 "somatella-formation" has been applied. It is well described by 

 Minchin and Thompson (1915) in the case of Tryyanosoma lewisi 

 (Fig. 118) as follows: 



B 



D 



Fig. 117. — Chlorogoniurti eiichlorum, formation of gametes. A, B, macrogameto- 

 cyte forming eight macrogametes; C, E,D, microgametocyte forming microgametes. 

 (From Doflein after Stein.) 



"The parasites when taken up by the flea {Ceratoyhyllus fasckitus) 

 pass with the ingested food into the stomach (mid-gut) of the insect. 

 In this part they multiply actively in a peculiar manner, not as yet 

 described in the case of any other trypanosome in its invertebrate 

 host; they penetrate into the cells of the epithelium, and in that 

 situation they grow to a very large size, retaining their flagellum 

 and undulating membrane, and exhibiting active metabolic changes 

 in the form of the body, which in early stages of the growth is 

 doubled on itself in the hinder region, thus becoming pear-shaped 



