PROCEEDINGS 



OF THE 



WASHINGTON ACADEMY OF SCIENCES 



Vol. IX, pp. 179-1S7. July 31, 1907. 



HEREDITY AND MENDEL'S LAW/ 

 By Charles B. Davenport. 



From its first appearance on earth the living substance has 

 moved like the growing roots of a tree from a single point, 

 without break in its continuity, but ever branching out in new 

 directions. This fundamental stream is the germ-plasm. At 

 intervals, as roots may send up shoots, so the germ-plasm pro- 

 duces the individual body or soma, whose primary purpose is to 

 nourish the germ-plasm and thus assist its further progress. 



The soma is important to the student of heredity because it 

 is the index of the composition of the particular germ-plasm 

 from which it arose. The study of somas shows that those aris- 

 ing from the same part of the germ-plasm are very similar ; 

 those from distant parts of the germ-plasm are very different ; 

 those nearer the starting point of any root are simpler in struc- 

 ture, while those arising more recently are more complex. 

 These differences of the soma prove that the germ-plasm 

 changes in structure and tends to become more complex. 

 These changes in the germ-plasm'constitute evolution, and the 

 study of the laws of change of this germ-plasm and the arti- 

 ficial control of such change constitute at the same time the 

 largest and most fascinating work of the modern biologist. 



Inside the germ-plasm complex movements are going on. In 

 the first place, the development of a soma at any point is usually 



' An address delivered under the auspices of the Washington Academy of 



Sciences, Tuesday evening, February 26, 1907, in the Hubbard Memorial Hall, 

 Washington, D. C. 



Proc. Wash. Acad. Sci., July, 1907. 179 



