222 BIOLOGICAL LECTURES. 



diverging only as we estimate the two classes of complemen- 

 tary causes unequally. The intra and the extra do not exclude 

 each other but coexist and cooperate from beginning to end of 

 development. 



I do not forget that there is an important distinction to be 

 kept in mind between the internal and the external factors. 

 Within the germ we have formed elements acting in organized 

 unison towards a definite end — that end being prescribed, not 

 teleologically, but constitutionally, as the fruit of all that 

 inheritance has preserved of ancestral progress. Without, we 

 have the conditions and influences of a boundless environment 

 — ether, air, water, earth, gravity, solar heat, light, and all the 

 rest. Some of these fluctuate from moment to moment, or 

 rise and fall periodically, while others appear to be absolutely 

 constant. They comprise food, conditions, and stimuli. 

 Broadly considered, they are common to all germs. They do 

 not act organically ; that is, they are not coordinated and 

 directed to specific ends. It is the germ that does all the 

 measuring, weighing, selecting, transmuting, distributing, co- 

 ordinating. All germs grow and multiply at the expense of 

 external conditions and influences; and so the internal and ex- 

 ternal are forever interchanging. 



While we distinguish between the formed and the wiformed, 

 we do not set one against the other as absolutely distinct and 

 inconvertible. On the contrary we insist that interchange is 

 of the essence of organic phenomena, and thus our position 

 contradicts the central idea of the old evolution, and at the 

 same time supplies epigenesis something more substantial to 

 build upon than spontaneity and spiritual agencies. 



Our difference is no longer measured by the distiuction 

 made between the formed and the unformed, but by inequali- 

 ties of emphasis which we apportion to the two sets of factors. 

 Our present standpoints differ from the old far more than 

 from each other. In some respects the extreme views of 

 to-day reverse the extremes of last century. The old evolu- 

 tion, denying the possibility of generation, was compelled to 

 maintain that whatever development adds to the organism comes 

 from external sources. Monstrosities and hybrid forms were 



