2i8 THE BEGINNINGS OF II FE. 



were watched on many occasions i. On the sixth day 

 many of the Monads had much increased in size, some 

 of the larger of them measuring tsW in length. 

 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 ^o W in diameter 

 (Fig. ^^^ b^ c, d). All stages were seen, between the 

 ovoid corpuscle ^ssW' in 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 from its periphyry. 



In other specimens the most easy and rapid alter- 

 nations were seen between the shape and mode of loco- 

 motion which pertains 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 amceboid movements, the extra vacuoles 

 would disappear, the shape of the Monad would be re- 

 sumed — and with it the lashing movements of the 

 flagellum which again gives rise to the rapidly-darting 



^ It took place mostly in a longitudinal, though occasionally in a 

 transverse direction. I have never seen the whole process occupy less 

 than twenty minutes. 



