168 LIFE: ITS NATURE AND ORIGIN 



strate cytoplasmic inheritance, even though V. Jollos produced 

 "Dauermodifications" in which cytoplasmic effects persisted through 

 hundreds of generations, and V. von Wettstein was able to keep some 

 hybrid mosses for fifteen years without indication that their cytoplasm 

 had been gradually reconstructed by foreign genes. Wettstein 

 classified components of the germ plasm (cytoplasm plus all particulate 

 units) as follows: (1) the genome, i.e., all genes carried by the chro- 

 mosomes; (2) the plastidome, arising from the properties of the plastids 

 themselves; (3) the plasmon, genetically effective portions of the 

 cytoplasm. 



Where prolonged and skillful experiments fail to secure a de- 

 sired result, the feeling grows that "it can't be done." Such a 

 despairing note is sounded by calling viruses "obligate parasites," 

 when the truth simply is that we have as yet been unable to find 

 a non-living medium for them. However, some kinds of viruses 

 are now cultivated on chorio-allantoic membranes of developing 

 hen's eggs, on a commercial scale for use in immunization. The 

 viruses of poliomyelitis and of the foot-and-mouth disease do not 

 grow on these membranes. 



Professor E. G. Conklin stated: 8 "The classic argument of the 

 Weismannians was that we can conceive of no mechanism by 

 means of which somatic changes can be carried back into the 

 germ cells, and therefore there is no such mechanism. Now the 

 fallacy of this argument is obvious; even if we could conceive of 

 no suitable mechanism for this purpose, this does not preclude 

 the existence of such a mechanism." As the all-pervasive phe- 

 nomena of catalysis became more and more recognized and under- 

 stood, it became evident that in catalysis we have what still seems 

 to be the only basic mechanism whereby we can explain the under- 

 lying chemical changes which directly or indirectly govern life 

 and its physical manifestations. Catalysis discloses the required 

 mechanism, which is not revealed by valid views of what happens 

 at higher structural and organizational levels, so that the very 

 terms used in expressing these views imply results rather than 

 mechanism. As Thistleton Dyer remarked in his address to the 

 British Association for the Advancement of Science at Bath in 

 1888: "Science will always prefer a material modus operandi to 

 anything so vague as a tendency." 



Everyone recognizes that the cytoplasm is a specialized milieu 

 in which and with which the genes and other inclusions function. 

 Chapter 9 considers the importance in differentiation of the mil- 



