CERCOMONAS AND TRICHOMONAS. 



239 



even so frequent (especially in moths and flies) that whole tracts of 

 the intestine are filled with them. 



Eeproduction is effected by division, which generally takes place 

 longitudinally, and is often so rapidly repeated that the young ones 

 remain for a time grouped close together. Dallinger and Drysdale 

 have also observed conjugation in the Monadinse. This is followed by 

 an encystation, in which the contents break up, and become moveable 

 germs, or countless, immeasurably small spores, which afterwards be- 

 come new Monadinse, and even at high temperatures (above 100 C.) do 

 not lose their power of further development. In individual cases other 



FIG. 119. Trichomonas batrachorum. (After Stein.) 



observers have also noted a quiescent state, which leads to the pro- 

 duction of countless little swarm-spores. 1 



The flagella, which vary very much in number and arrangement, 

 furnish us with the best standpoint from which to consider the indi- 

 vidual characteristics of the various genera. But since a very strong 

 magnifying power is necessary to establish the exact nature of these 

 conditions, many mistakes have been made, which have been specially 

 disastrous in the identification of the species occurring in man. The 

 latter belong, so far as we accurately know them, to two very widely 

 distributed genera, Oercomonas and Trichomonas. The former of 



1 [Recently the independence of the Monads (at least of the parasitic forms) has been 

 several times questioned, and the attempt has been made to regard them as swarming 

 conditions of Amcebce, especially in Cunningham's paper (Quart. Journ. Micr. Sci., N.S., 

 vol. xxi., p. 234, 1881). The Cercomonads are said, after encapsulation, to become A mcebce, 

 which fuse together in large numbers after losing their power of movement, and form 

 considerable masses or even true sporangia. I?. L.] 



