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THE AMEBIC AN NATURALIST [Vol.XLIV 



separated from the part of the organism in which these 

 substances are produced. Thus the greater development 

 of horns in the males of certain species is supposed to be 

 due to hormones produced in the testes. 



Any organ, tissue, substance or cell organ which thus 

 has the power of influencing the course of development, 

 I propose to call a "teleone." This word is from the 

 Greek teleo, which means make, or accomplish. Teleones 

 occurring in the egg, and presumably derived directly 

 from the previous generation, may be called primary 

 teleones. Those that arise during the course of develop- 

 ment may be called secondary teleones. The manner in 

 which primary teleones function in heredity has already 

 been indicated. In a simple Mendelian character differ- 

 ence we are thus dealing, not with two unit characters, 

 nor with the presence and absence of a single unit char- 

 acter, but with a difference between two teleones. 



Under this hypothesis, transmission becomes, not the 

 transmission of characters as such, but the transmission 

 of cell organs having functions which determine character, 

 or which influence development. This hypothesis may 

 properly be called the teleone hypothesis. 



A word about species crosses. We may imagine that, 

 in species not closely related, the corresponding teleonic 

 functions all differ more or less; hence we should not ex- 

 pect many simple Mendelian phenomena in such crosses. 

 Again, in wide crosses, it will probably happen frequently 

 that the chromosomes brought together will be so dis- 

 similar that they do not act together in the usual manner, 

 especially in the reduction division. We should expect 

 Mendelian phenomena only in cases where homologous 

 chromosomes go through synapsis and reduction in a 

 formal manner. 



Finally, when character differentials relate to anything 

 other than chromosomes, Mendelian splitting should not 

 occur. I would therefore suggest that some of the char- 

 acter differentials studied by Castle in rabbits are due to 

 cytoplasmic differences, or at least are not due to the 

 chromosomes. 



