508 THE BEGINNINGS OF LIFE. 



ordinaire, et elaborer ses vesicules internes (Fig. 4), qui 

 deviennent huileuses, qui se scindent (Fig. 5) et se 

 reve'siculisent, jusqu'a ce que le degre d'animalisation 

 convenable soit atteint, et propre a donner naissance 

 aux Rotatoires les plus varie's, selon la taille et la forme 



FIG. 91. 

 Conversion of Encysted Euglena into a Rotifer. (Gros.) ( X 500.) 



a. Encysted Euglena of an oval form, and pointed at one extremity. 



b. Similar body after its contents have become animalized and converted 



into an embryo Rotifer. The whole mass is now larger and the 

 investing envelope thinner, though it still remains pointed at its 

 posterior extremity. 



de Foeuf.' So multitudinous are the forms of Rotifera 

 which he has seen emerge from these transforming 

 Euglenae that Dr. Gros says : c I/on peut se demander 

 s'il existe une forme de Rotatoire qui ne puisse deliver 

 des Euglenes directement ou par d'autres transforma- 

 tions 1 .' Thus, in addition to the numerous kinds of 



1 Such notions are certainly in harmony with facts long known con- 

 cerning the habitats of Rotifers. Speaking on this subject Pritchard 

 says (' Infusoria,' 4th ed. p. 653) : ' Usually they must be sought for in 

 a systematic way, without any external indications whether a pool will 

 prove productive or barren. We have, however, rarely been disappointed 



