336 WILLIAM LAWRENCE TOWER, 



is the relation in this complex of that which makes for the elabora- 

 tion of tyrosin and tyrosinase in melanogenesis. What is it in 

 this complex that localizes in a definite area the appearance of 

 a pigment? What is it that combines into a definite pattern a 

 series of attributes, some of which can be shifted and rearranged 

 in the processes of hybridization? The problem of the constitu- 

 tion of the gametes of that which makes for form, for localiza- 

 tion, for pattern, etc., is the fundamental problem; and as long as 

 we fail to see clearly what the constitution of living matter is, such 

 phenomena as these which we have been discussing must remain 

 more or less superficial in our knowledge of the living organism. 



There is nothing in the behavior of these attributes, in our 

 ability to shift them and make new combinations, which, of 

 necessity, commits one to any of the doctrines of preformation 

 in pangenes or biophores, or to oneness of constitution and ortho- 

 genetic destiny. The situation, as regards alternative behaviors, 

 should be free from the bias of biological orthodoxies, and to re- 

 •gard the organisms with which we are dealing as so many com- 

 plex physical substances whose composition we are investigating, 

 and among which we are seeking to determine the limits and 

 laws of combination, will give the most rapid progress towards 

 the end of a better understanding of the larger problems of the 

 evolution of living substance. 



Department of Zoology, 



The University of Chicago, 

 April I, 1910. 



BIBLIOGRAPHY. 

 Bateson, W. 

 1902 Reports to the Evolution Committee. Report No. i, pp. 1-160. 

 1909 Mendel's Principles of Heredity. Cambridge University Press, XIV., 

 396 pp. 

 Castle, W. E., et al. 



1909 Studies of Inheritance in Rabbits. Carnegie Institution of Washington 

 Publications, No. 114, pp. 68, 4 pis. 



Cuenot, L. 

 1902 L'Heredite de la Pigmentation chez les Souvis. Arch. Zool. Exp., i (Notes 

 et Revue), pp. 33-41. 

 Davenport, C. B. 



1910 Inheritance of Characteristics in the Domestic Fowl. Carnegie Institu- 

 tion of Washington Publications, No. 121, pp. 100, 12 pis. 



