500 THE BEGINNINGS OF LIFE. 



Remarks upon some of the Developmental Tendencies of 

 Ciliated Infusoria ^ and upon the different Modes of 

 Origin of Rotifers^ Tardigrades^ and Nematoids. 



But just as the Ciliated Infusoria are often only higher 

 developmental states of portions of living matter which 

 have previously existed in a simpler condition, so they 

 themselves very frequently become transformed into 

 more complex living types. Dr. Gros pointed out these 

 highly important facts more than twenty years ago, 

 when, after speaking of Actinophrys, he said : — ^ Les 

 utriculeux cilies, Vorticelles, Plsesconiens, Oxytriques, 

 Kerones, Dileptus, Coccudina, Nassula, etc, recon- 

 naissent aussi une origine vesiculaire vegeto-animale. 

 En general, ils tendent aussi a I'ascendance et beau- 

 coup (pourquoi pas tous ?) se convertissent en Rota- 

 toires minuscules, qui peuvent continuer I'echelle as- 

 cendante ou rester dans le cercle des Cilies. Bon 

 nombre d'Utriculeux, selon leur deriyance, s'en tien- 

 nent a tcurner dans leur monde proteen et tortueux. 

 Les agents exterieurs^ la forme et la grandeur des vases 

 sont tres-puissants sur leur evolutions.' 



The various forms of Ciliated Infusoria, in fact, 

 whose mode of origin may be so different on different 

 occasions, after living for a time a life of great activity, 

 during which they may give birth to other similar 

 creatures by processes of fission and external or internal 

 gemmation, at last encyst themselves in a manner 

 which has been so often described. Within this cyst 



