Vol. XVIII May, igio. . No. 6 



BIOLOGICAL BULLETIN 



THE DETERMINATION OF DOMINANCE AND THE 

 MODIFICATION OF BEHAVIOR IN ALTERNATIVE 

 (MENDELIAN) INHERITANCE, BY CONDITIONS 

 SURROUNDING OR INCIDENT UPON THE GERM 

 CELLS AT FERTILIZATION/ 



WILLIAM LAWRENCE TOWER. 



CONTENTS. 



Page 



Introduction. 



The Point of View 285 



Material 289 



Experiments in Analysis 293 



Crosses Between L. signaticollis and L. diversa 293 



Crosses Between L. signaticollis and L. undecimlineata 296 



Experiments in Synthesis 307 



Crosses Between L. undecimlineata and L. sig7taticollis 308 



Crosses Between L. undecimlineata, L. oblongata and L. muUitaniata. . . . 312 



Discussion 323 



Neo-Mendelism — The Factorial Hypothesis and Germ-plasm Theories. 323 



Dominance — Dominance discussed on basis of examples in this paper. . 329 



Relation of External Conditions to Dominance 333 



Conclusion 335 



Bibliography 336 



Explanation of Plates 338 



Introduction. 



The Point of View.— The mutation theory of DeVries, th^ 

 rediscovery of Mendel's paper on hybrid peas, and the work of 

 the Mendelian hybridologists have focused the attention of biolo- 

 gists upon the characters of organisms as basal units for investi- 

 gation in the effort to understand the modus operandi of evolu- 

 tion. The most conspicuous outcome is the growth of the "unit 

 character" hypothesis, which, in the main, has been adopted 

 by the Neo-Mendelians as the fundamental assumption necessary 



1 A paper presented at the meeting of the American Naturalists in Boston, 



Dec, 1909. 



285 



