GENERAL CHARACTERS 37 



surface which is directed downwards in the ordinary 

 position, and bears the second or trailing flagellum, and an 

 opposite or dorsal surface directed upwards. 



Often instead of swimming freely in the fluid a Hetero- 

 mita is found anchored as it were to a bit of the decompos- 

 ing substance by its ventral flagellum as in A 1 . Under 

 these circumstances it is in constant movement, springing 

 backwards and forwards by alternately coiling and uncoiling 

 the attached ventral flagellum. The general character of 

 the movement will be readily understood from the figure in 

 which A 1 shows the monad with coiled flagellum, A 2 after it 

 has sprung forward to the full extent of the flagellum. It 

 is from this curious habit that the name " springing monad ' 

 is derived. 



Towards the posterior end of the body is a nucleus (mt), 

 and at the anterior end a contractile vacuole (c. vac}. There 

 is no trace of an investing membrane or cell-wall, and the 

 protoplasm is colourless. Also, as is invariably the case 

 with organisms devoid of chlorophyll, there is no starch. 



In considering the nutrition of Heteromita it is necessary, 

 first of all, to take into consideration the precise nature of 

 its surroundings. It lives, as already stated, in decomposing 

 infusions of animal matter. Such infusions contain proteids 

 in solution, in part split up by the process of decomposition 

 into simpler compounds some of which are diffusible ; this 

 process is due, as we shall see hereafter (Lesson VII I. ), to 

 the action of the minute organisms known as Bacteria, 

 which are always present in vast numbers in putrescent 

 substances. 



As Heteromita contains no chlorophyll its nutrition is 

 obviously not holophytic. Observation seems to show 

 pretty conclusively that it is not holozoic ; apart from the 



