26 BIOLOGICAL SOCIETY OF WASHINGTON. 



reproductive elements, though doubtless many times larger 

 than any chemical molecule, even the most complex, such as 

 those of protein and other organic compounds, are doubtless 

 still far too minute to be observed by the highest powers of 

 the microscope, and if the entire history of the formation of a 

 new organic being is ever to be learned it must be by a suc- 

 cessful study of the actions of such minute objects. But this 

 is infinitely more difficult than the study of the actions of 

 inorganic elements, since they take place within an organism 

 whose destruction destroys their vital character. 



In view of the history of the less complex sciences it is 

 natural that biologists should insist that the phenomena of 

 heredity are due to the activities of the ultimate material 

 reproductive elements, and not to any vague and occult force 

 or deus ex niachina. Consequently we find that the only 

 theories of heredity that have been put forth have been based 

 on this assumption. 



One of the earliest, and certainly the most celebrated of such 

 theories is Darwin's pangenesis, published in 1867.* Accord- 

 ing to this theory, which is doubtless familiar to most of you, 

 the ultimate reproductive elements, called gem mu/es, are given 

 off from the cells of all parts of the body and collect in the 

 germ-cells and sperm-cells, so that the fertilized ova contain 

 literal representatives of every organ and every part of both 

 parents, which in the new being return to their respective 

 locations and cause the repetition in each of the exact qualities 

 possessed by the parental organs or parts, subject, of course, 

 to the modifications due to a conflict or cooperation between 

 the genimules of the two parents, equalizing a character where 

 they are different, and emphasizing it where they are alike. 



* Variations of Animals and Plants under Domestication. Vol. II, 

 Chaps. XXXVII, XXXVIII. 



