PROTOPLASM 



37 



yield apparently the same substances, differ nevertheless from 

 each other as much as the active x individual differs from the 

 active y individual. The organization of the protoplasm of the 

 two forms must be radically different. These differences of 

 organization are supposed to lie in the molecular make-up of 

 the proteins of which their protoplasms are composed. 



In its normal medium an encysted organism emerges as an 

 active individual of its own species, and nothing else can happen 

 so long as the environment remains the same. Its protoplasmic 

 organization as an adult, however, is different from that of its 

 protoplasmic organization when encysted, and here is where our 

 analogy with the automobile breaks down. The parts of an 

 automobile, when active, are the same as the parts when static, 

 but the parts (chemical substances) of an organized living thing 

 undergo marked changes with the activities in which they take 

 part. Thus when water and oxygen are introduced through the 

 cyst membrane of an en- 

 cysted Uroleptus halseyi, 

 new structures — motile 

 organs, cell mouth, and 

 a different shape of the 

 body — appear, which 

 were not present before 

 (Fig. 18). These new 

 structures are due to 

 changes brought about, 

 presumably, by the oxi- 

 dation of certain sub- 

 stances in the outer zone 

 of the protoplasm of 

 the encysted organism, and these changes are always the same 

 for the same species. Oxidation results in the breakdown of 

 such substances, and in the transformation of the latent energy 

 of their combination into a dynamic form of energy expressed 

 by movement. New substances are formed, some of which 

 may be responsible for the motile organs or the various other 

 structures of the adult. All of them, however, react with 

 the other substances of the protoplasm, and so set up those con- 

 nected chains of protoplasmic activities, destructive and con- 



Fig. 18- 



-THE DERIVED ORGANIZATION OF 

 UROLEPTUS HALSEYI 



A group of individuals showing little more than a chain 

 of macronuclei and the general cigar shape of the body. 



From a photomicrograph by the autlior 

 Magnification, 600 



