1872.] 



Modes of Origin of Infusoria fyc. 



247 



the Monads had much increased in size, some of the larger of them mea- 

 suring -j-g-Vo " m l eo gth. Others had lost their flagellum, and were existing 

 in the form of ovoid or rounded corpuscles, which were motionless, though 

 still provided with a vacuole, and now also with a solid nucleus about 

 TooW m diameter (fig. 3, b, c, d). All stages were seen, between the 

 ovoid corpuscle -3 3V0 ' m length and a much larger Amoeba of the kind 

 just described, which was either motionless or else, at intervals, exhibited 

 slowly evolved and blunt protrusions at its periphery. 



In other specimens the most easy and rapid alternations were seen be- 

 tween the shape and mode of locomotion which pertain to Monads and those 

 which are characteristic of Amoebse. Monads which had been previously 

 in active motion would at times come to a state of rest, develop two or 

 three vacuoles in their interior, and behave in all respects like an Amoeba, 

 save for the presence of the now languidly moving flagellum. After remaining 

 in this state for a variable time, some of them would just as abruptly cease 

 to display the amoeboid movements, the extra vacuoles would disappear, the 

 shape of the Monad would be resumed, and with it the lashing movements 

 of the flagellum, which again gives rise to the rapidly darting gyrations of 

 the organism. Whilst in the amoeboid state the changes in shape were 

 moderately rapid ; though two or three organisms were watched, one por- 

 tion of which remained rounded and apparently attached to the glass, 

 whilst the opposite extremity threw out and retracted comparatively long 

 processes with lightning-like rapidity — some of them being filiform, like the 

 ordinary persistent flagellum*. 



On the seventh day thousands of the motionless spheroidal Amoebse 

 were seen, which had much increased in size. They were now as much as 

 ■ a o " in diameter, and displayed one or more vacuoles (fig. 3, d). Each 

 one contained a distinct nuclear particle, though there was an almost com- 

 plete absence of granules, the body substance being quite pellucid. Some 

 organisms of the same kind, though rather smaller, contained the ordinary 

 granules in their interior and also exhibited slow amoeboid movements ; 

 whilst many Monads of the same size and general appearance were seen 

 exhibiting amoeboid changes of form, though they had not yet lost their 

 almost motionless flagellum. 



On the eighth day there were myriads of active Amoebse around every 

 portion of the pellicle which was examined ; they were, in fact, at this pe- 

 riod, almost as numerous as the Monads. Great numbers also existed in 

 the spherical motionless condition. 



On the ninth day the pellicle began to assume a brownish colour on the 

 surface, owing to the enormous development of minute brown fungus-spores j\ 

 Portions of the pellicle were also separating and beginning to shrink, whilst 



* The rapidity with which such processes were emitted was similar to what was no- 

 ticed at p. 245. 



t Very similar to those represented in fig. 4, e. 



t2 



