Zld PHYSIOLOGY OF THE INVERTEBRATA. 



very slowly. This movement, which only occurs occasionally, 

 is clue to the contractile nature of its body. 



The Flagellate Infusoria are provided with flagella ; these 

 are appendages which have a dual function, being organs of 

 locomotion as well as of prehension. " The Protozoan Avith 

 its flagellum executes the most varied movements, moving 

 first in one direction, then in another, and in different 

 planes ; sometimes the animal curves about entirely ; but 

 most frequently, when it uses the flagellum as an organ of 

 prehension, it extends the whole length of the organ ; the 

 basal part remaining completely immovable and rigid, while 

 the free end alone executes movements destined to drive food 

 to the mouth, which is generally situated at the base of the 

 flagellum." In certain genera of the FlagcUata (among these 

 the Pcridinecv), there are organisms which have the power of 

 throwing off their flagella before entering into a dormant 

 state ; and they can as readily regenerate these important 

 organs. (Biitschli.) 



" In Antlwphysa, there are two motor organs — the one a 

 stout and comparatively stiff flagellum, which moves by 

 occasional jerks, and the other a very delicate cilium, which 

 is in constant vibratory motion." 



Drs. Dallinger and Drysdale* (who have so thoroughly 

 worked out the life-history of several species of JNtonads or 

 FhifjeJlata) state that in some of these organisms there is a 

 peculiar structure, which is intimately connected with the 

 bases of the flagella, this appears to be muscular and is the 

 probable cause of movement in the flagella. They also state, 

 " that in every instance where there was only one flagellum, 

 or where the two arise and move from the same point, their 

 insertion in the body-sarcode was always in front ; so that 

 the flagellum or flagella had a pulling motion like that of the 

 paddle of an ancient coracle ; never the pushing motion from 

 the stern like the sculling or rowing of a modern boat. This 



* Monthly MicroscopicalJo^irnal, 1874, p. 264; and 1875, p. 190. 



