570 THE BEGINNINGS OF LIFE. 



derive additional support from the fact that even 

 amongst those groups of animals or plants in which 

 ^alternate generation' largely prevails, some species 

 undergo a direct process of development. No sort of 

 explanation of these apparent anomalies has, as yet, 

 been offered. But now it seems that they are ren- 

 dered in some degree explicable by what we have 

 learned concerning the transformations of some of the 

 ephemeromorphs. We may find, for instance, a Ro- 

 tifer originating directly from the metamorphosis of a 

 large Euglena, or of a large mass of protoplasm and 

 chlorophyll which separates from the wall of a Nitella- 

 filament; whilst if a small Euglena, or a small mass 

 of Nitella protoplasm and chlorophyll undergoes trans- 

 formation_, a more or less similar Rotifer may ultimately 

 be developed, though in this case only after the organism 

 directly produced from the originally smaller matrix 

 had passed through certain metamorphic changes. 

 Such a product of transformation may appear succes- 

 sively as an Actinophrys, an Amoeba, and a Ciliated 

 Infusiorum (and during each of these stages agamic 

 multiplication may take place) before passing, as a 

 much larger mass, into that final state of encystment 

 from which it is to emerge in the form of a Rotifer. 

 Such double sets of phenomena are very prone to occur 

 amongst the ephemeromorphs, and are remarkably analo- 

 gous to the direct development of some few eggs of Disto- 

 mata or Medusse as compared with the cyclical develop- 

 ment of others by processes of ^ alternate generation.' 



