INTRODUCTION 45 



the Protozoa must be traced back to the chemical nature of the 

 proteins and to their relations and interactions with other substances 

 in protoplasm. Types which have a similar chemical and physical 

 make up, with similar metaplastids and plastids, are practically 

 identical in form and structure and we recognize them as distinct 

 species. Variations in chemical composition, be they ever so little, 

 must result in different chemical reactions and products, and in 

 corresponding variations in form and structure of the organism, 

 and these variations furnish the basis for classification. 



Under normal environmental conditions the reactions among the 

 varied substances in protoplasm of the same species, with their 

 products and arrangement of these products, are individual and 

 invariable. Furthermore, the entire organism partakes of this indi- 

 viduality. A fragment of Stentor obtained by cutting or by shaking 

 cannot be distinguished from a similar fragment of Dileptus, yet 

 the former regenerates into a perfect Stentor, the latter into a per- 

 fect Dileptus. Or an encysted Uroleptus mobilis is morphologically 

 identical with an encysted Didinium nasutum; both are apparently 

 homogeneous balls of undifferentiated protoplasm; the one emerges 

 from the cyst and develops with the characteristic differentiations 

 of Uroleptus, the other of Didinium. In short, the homogeneous 

 ball representing Uroleptus is as specific and different from the 

 homogeneous ball representing Didinium, as the adult Uroleptus is 

 different from the adult Didinium. We may speak of this undiffer- 

 entiated chemical and physical make-up as the fundamental organ- 

 ization of the species, in a sense similar to the architectonik of 

 Driesch. The adult characteristics result from the interactions of 

 the specific proteins, carbohydrates, salts, water, etc., among 

 themselves and with the environment, and represent what we may 

 call the derived organization. 



Organization in the above sense is not only specific but is con- 

 tinuous from generation to generation, and has come down through 

 the ages subject, however, to modifications and changes through 

 interaction with the environment or through changes coming from 

 within as in amphimixis. 



While organization is continuous the actions and reactions going 

 on within it are discontinuous. More or less prolonged periods of 

 rest are characteristic of all living things, best exemplified in the 

 case of spores, eggs, encysted Protozoa and seeds. At such times 

 the organization is static; the chemical substances making up the 

 specific organization are present but quiescent, or at least, in the 

 absence of water, relatively inactive. A striking illustration is 

 afforded by the phenomenon of desiccation in some types of animals, 

 e. g., rotifers, which has been known for decades. For some years 

 I had on my shelf a bottle of minute amorphous granules which 

 appeared like specks of dust under the microscope. After placing a 



