122 SYMBIONTICISM AND THE ORIGIN OF SPECIES 



The established mechanism of heredity permits the 

 development of variations in organisms, but these varia- 

 tions, apparently do not lead to the production of new 

 species. These variations may be of a retrogressive nature, 

 resulting in the loss of parts or characters, but apparently 

 no fundamentally new character is produced by a rearrange- 

 ment or loss of genes. It apparently is necessary that 

 "new" genes be added to chromosomes in order to produce 

 a fundamentally new character. 



How, then, does Symbionticism affect the accepted 

 mechanism of heredity and correlate it with our ideas of 

 organic evolution? The conception that mitochondria 

 may be involved in the transmission of hereditary charac- 

 ters was enunciated by Meves in 1908. A few other inves- 

 tigators accepted this point of view, but the advances in 

 genetics and cytology, and particularly the introduction of 

 the idea of genes, made this position apparently untenable, 

 so that httle or nothing is heard of this hypothesis today. 

 It is interesting in this connection to note that certain ac- 

 tivities are locahzed in the cytoplasm of egg cells of some 

 species of animals before the first cleavage takes place. 

 ''Localizing activities thus made visible have been studied 

 by many observers, prominent among them Driesch, 

 Boveri, LilHe and Conkhn" (Wilson, '25). Conkhn ('05) 

 demonstrated three strata in the egg of Styela partita im- 

 mediately following the entrance of the sperm. From the 

 three strata — an upper clear, a lower gray and a middle 

 yellow — ectoblast, entoblast and mesoblast are formed, 

 respectively. Duesberg investigated this problem in Ciona, 

 and was able to show a variation in the amount of mito- 

 chondria in the three strata. It is difficult from the amount 

 of work that has been done, to determine what the signifi- 

 cance of these phenomena may be. Obviously, the varia- 

 tion in the amount of mitochondria in the three regions of 

 the developing ovum signifies something. It does not 



