THE BEGINNINGS OF LIFE. 499 



Again, simple forms like Cyclidium, Enchelys, and 

 others, which may have been derived from Monads 

 or Amoebae, are also, in all probability, prone to assume 

 very different characters when they exist under diverse 

 conditions, so long as these conditions are not un- 

 favourable to their growth 1 . 



All the evidence which has now been brought forward 

 concerning the Ciliated Infusoria entitles us to believe 

 that they may be derived either from lower forms such 

 as Monads, Amoebae, and Actinophrys ; or that they may 

 arise from the direct transformation of masses of 

 animal or vegetal tissue existing in a separate condition, 

 or else from parts of larger organisms which have re- 

 cently individualized themselves. Whilst these trans- 

 formations of larger animal or vegetal masses into 

 Ciliated Infusoria may take place immediately, some- 

 times they occur only after previously -lower meta- 

 morphoses into Amoebae or Actinophrys. The different 

 forms ultimately assumed would seem to depend in the 

 main upon the intrinsic molecular properties of the 

 matter of which they are composed ; whilst the extreme 

 variability of these forms tends to imply that the 

 molecular composition of such matter is modifiable to 

 an extraordinary extent. 



1 Thus Prof. Schaaffhausen speaks of Amoebae developing into speci- 

 mens of Cyclidium and Chilodon, and of the conversion of the latter 

 forms into Paramecia ; though, as he says, the metamorphoses ' ne se 

 font pas toujours de la meme maniere.' (' Cosmos,' t. xxii. p. 635.) 

 K k 3 



