472 THE BEGINNINGS OF LIFE. 



to show that other forms of Ciliated Infusoria are also 

 frequently produced by the further growth and develop- 

 ment of Monads and Amoebae. 



It has been already stated that the embryonal spheres 

 which are so abundantly produced within the filaments 

 of a dying Nitella may segment into Flagellated 

 Monads, or that they may be wholly transformed either 

 into Amoebae and Actinophrys, or into some one or 

 other of the forms of Ciliated Infusoria 1 . I have, 

 however, on several occasions been able to watch the 

 stages by which these Flagellated Monads after in- 

 creasing in size become converted into Amoebae; 

 whilst the latter, after undergoing some increase in 

 bulk, become motionless and lapse into more or less 

 ovoidal forms. The motionless bodies thus produced 

 gradually protrude cilia from various parts of their sur- 

 face, and are very similar to the smaller embryonal 

 spheres of Nitella, which also develop at once into 

 various forms of Ciliata 2 . In both cases the cilia that 

 are at first protruded are motionless, and they subse- 

 quently move in a slow and languid manner, before 

 vibrating with sufficient rapidity to produce active 

 movements of the whole organism. The Monads 

 developed from the external vesicles of transforming 

 Euglenae 3 , and which have been shown to be almost 

 interchangeable with Fungus-germs, are also frequently 

 seen to undergo similar developmental changes. They 

 increase in size, the nuclear body breaks up into many 

 1 See pp. 402-404. * See Fig. So, c, c', d, a'. 3 Sae p. 437. 



