46 BIOLOGY OF THE PROTOZOA 



few of these granules in water each of them would become an active, 

 living rotifer in an hour or so. Here organization was present 

 but inactive, and activity began with the absorption of water and 

 with oxidation. The rotifer in the active state is the same rotifer 

 that it was in the dried condition, so far as organization is concerned, 

 but it differs in that the organization is now in action. It is a 

 difference of the same nature as that between an automobile stand- 

 ing in the garage, and the same automobile travelling 30 miles an 

 hour. The organization is in action in both moving rotifer and mov- 

 ing automobile; is static in the dried rotifer and in the standing 

 machine. 



The automobile simile, however, will not stand analysis. The 

 parts of the machine are little changed by activity and the organ- 

 ization remains the same throughout its period of usefulness. With 

 a living thing, on the other hand, the chemical and physical make up 

 changes with every activity and, as a result of such activities, the 

 protoplasmic organization itself will change. An encysted Uroleptus 

 is a motionless and apparently a homogeneous ball of protoplasm; 

 an hour later it is an elongate, cigar-shaped organism with special- 

 ized motile organs in the form of membranelles and cirri, and its 

 contractile vacuole pulsates with rhythmical regularity as it moves 

 actively about in the water. The organization has undergone a 

 change in this brief period; the first indication is the swelling and 

 enlargement of the cyst wall, evidently by the absorption of water; 

 oxidation probably occurs and substances already present, or new 

 substances formed as a result of this initial oxidation, are responsible 

 for the newly-developed structures or derived organization not 

 present before. Such structures, however, are the morphological 

 expression of the adult organization and their formation corresponds 

 to the development and differentiation of the metazoon egg. 



Continued activity involves other and still more subtle changes in 

 organization; some of these are evident in individual life between 

 division periods; others are evident only in a long series of individuals 

 constituting a life cycle. These will be more fully treated in Chap- 

 ters VII and VIII. 



Other changes in organization may be brought about by environ- 

 mental conditions; or they may be brought about by changes in 

 one or more of the substances constituting the protoplasm of the 

 species, as when amphimixis introduces a new combination of chro- 

 matin into the organization. These are undoubted factors in the 

 phenomena of adaptation and probably play a part in the orig- 

 ination of new species and types. 



Consideration of these and of similar activities in living proto- 

 plasm lead to questions regarding the nature of life and the nature 

 of vitality. Should we use the two terms life and vitality as syno- 

 nyms? We are very apt to speak of life as activity, or to say that 



