Conclusions and Theoretical 241 



of the genie system under the conditions in which they are operating." 

 One such interaction is given when alternative genie actions in the 

 same cell are decided by a specific cytoplasmic condition, as is the 

 case frequently in sex determination. Regarding the self-duplicating 

 parts of the cytoplasm, he feels sure that kinetosomes, plastids, and 

 probably mitochondria are such, though I believe that we can con- 

 sider these (except mitochondria) as specific features of certain cells 

 which can hardly be put in the same category as the general hereditary 

 properties of the cytoplasm. Sonneborn expects the main emphasis 

 in the future to be on a particular self -perpetuating molecular pattern, 

 which could include the surface of plastids and mitochondria as well 

 as the fibrillar protoplasm. Up to this point these views of Sonneborn 

 are borne out by the material reviewed, and in general are not 

 diflFerent from the conclusions presented here with the individual facts. 

 Recently he goes a step farther in regard to mitochondria (1955). 

 I quote: "Taken altogether, the various lines of evidence discussed 

 above raise the possibility — to put the matter cautiously — that the 

 mitochondria will prove to be a physical basis of normal cytoplasmic 

 inheritance — a view that has a long history . . . The theoretical 

 importance of this possibility is far greater than the already well- 

 estabhshed role of chloroplasts in cytoplasmic inheritance, for mito- 

 chondria, unlike chloroplasts, are common to all organisms, animals 

 as well as plants." I have enlarged sufficiently upon this subject and 

 shown that it is not advisable to call mitochondrial (and plastid) 

 conditions and their change cytoplasmic heredity (see II 2 E b). 



Unfortunately, as I look at it, Sonneborn is still in favor of 

 speaking of plasmagenes, which includes all self-perpetuating and 

 mutable plasma constituents, such as plastids and mitochondria but 

 also kinetosomes, centrioles, and even kappa particles. "Meanwhile I 

 shall employ the term plasmagene for those cytoplasmic structures 

 known to manifest genie properties, however infelicitous this may 

 seem when applied to bodies large enough to be microscopically 

 visible" (Sonneborn, 1950). One might say that a discussion of this 

 attitude amounts to semantics or is purely academic. Sonneborn him- 

 self holds this view on the question whether kappa particles and 

 "genoids" are viruses or proviruses (Darlington), both being border- 

 line cases. This view would have been correct twenty years ago. Today 

 the situation is that the plasmagene terminology may induce those 

 not acquainted with the facts and their interpretations, and also those 

 whose enthusiasm gets the better of their cool thinking, to talk and 

 write about plasmagenes as if they were a well-established counter- 



