372 THE EVOLUTION THEORY 



H'ollulur t)r<j^anisins may therefore often consist of single biophors, so 

 that in this case 'the conception of ))iophors Avonld coincide with that 

 (if tleti'iniinants. In innlticeHular organisms, on the other hand, 

 I should Ik- inclined on the wliole to picture the determinant as 

 ,1 group of liiopliors, -which are hound together by internal forces to 

 form a higher vital unity. '^Fhis determinant nnist live as a whole, 

 that is, assimilate, grow, and nuiltiply by division, like every vital unit, 

 and its liiophors nuist be individually variable, so that the separate 

 parts of a cell controlled by them may also be capable of transmissil)le 

 \ariation. That they are so, every highl}^ differentiated cell of 

 a higher animal teaches us ; even the smelling-hairs of a crab exhibit 

 a stalk, a terminal knob, and an internal filament, and many muscle-, 

 nerve-, and gland-cells are much more complex in structure. 



