328 WILLIAM LAWRENCE TOWER. 



patible with a behavior in gametogenesis that would result in 

 mechanical separation into unlike masses of germinal substance. 

 No idea is expressed or implied in this conception of the nature 

 of the physical state which conditions anything in the germ plasm, 

 nor must the fact be lost sight of that this is a proximate con- 

 ception of germinal substance and not an ultimate. At present 

 in biology we have no business with ultimate conceptions, and 

 the two thus far attempted of germinal constitution — the "par- 

 ticulate conception" and the "crystalline entity" are both equally 

 dismal failures and equally useless as working hypotheses. 



The conception herein set forward recognizes the following 

 facts as regards organic constitution: 



I. That there is in organisms a form basis, relatively unalter- 

 able as regards symmetry, pattern and arrangement of parts. 



8. That there are in organisms an array of attributes capable 

 of variation, but blending in heredity, forming blends and inter- 

 mediates. 



3. That there are in organisms an array of attributes which 

 can exist only in a definite state of stability — they are either 

 there or not there. 



4. That there are in organisms characters that by crossing can 

 be replaced by other more or less similar but different characters. 



These four classes of attributes in some manner are conditioned 

 by physical forces in the germ-plasm, and are, as far as we can 

 perceive, the product of the past interactions between the germi- 

 nal substances of past generations, and between these substances 

 and the conditions of their existence and activity. Two chief 

 series of physical events are at work; the series of events charac- 

 teristic of any germinal substance — the product of its past his- 

 tory, the genetic forces — and the interaction of this sub- 

 stance with new germinal substances under the dynamic action 

 of surrounding or incident forces. It follows from this that any 

 germ cell is an epigenetic product of the two series of events neces- 

 sary to the production of fertilized eggs and the resultant soma- 

 germ complex, and the subsequent germinal changes may be large 

 or small, in one or many of an unknown number of possible 

 directions of modification; and while consequent somatic or germi- 

 nal attributes may to us appear as either continuous or discon- 



