History of the Theory of Heredity. 41 



terms of force. The statement does not help us at all 

 to picture to ourselves the essential hidden structure 

 of the egg, the organization upon which its wonderful 

 properties depend. 



Jager has recently brought forward an hypothesis 

 which seems at first sight to be a satisfactory epigenesis 

 hypothesis, but examination shows that this too, like 

 Eaeckel's perigenesis hypothesis, must be turned into 

 an evolution hypothesis before it can be accented. 



The following extract from his paper (" Zur Pan gene- 

 sis," von Prof. Dr. C. Jager. Kosmos iv. 376. 1879) 

 gives, I believe, a fair statement of his views. 



"Each organ and tissue of an animal or plant con- 

 tains, in the molecules of its albumen at least, a specific 

 flavor-and-odor-substance (Duft-und-Wiirzestofl:) which 

 we can easily recognize by our chemical sense, for each 

 organ of an animal has its distinctive flavor. Whenever a 

 full-grown animal experiences hunger, decomposition of 

 albumen takes place in all its organs and tissues, so that 

 their various flavor-and-odor-substances, that is their 

 soul-substance (Sezenstoffe), become free, and penetrate 

 to all parts of the body. 



"Now, if there exists in any part of the body proto- 

 plasm with the power to attract this substance, this pro- 

 toplasm acquires in this way its vires format ivce. 



" I have already referred with emphasis to the em- 

 bryological fact that the formation of the reproductive 

 elements takes place at a very early stage in the embry- 

 onic life of an animal, and I have designated this as 

 the reservation of germinal protoplasm. As soon as the 

 embryonal cells of the developing animal have become 

 specialized into ontogenitic and phylogenetic cells, the 

 following will occur. Whenever any decomposition of 

 albumen occurs in the developing organism, from lum- 



