No. 3-] PHENOMENA OF SEX-DIFFERENTIATION. 493 



parts of the organism. The organism is either a male or a 

 female, not by the difference of " primary sexual characters " 

 alone, but by the difference which saturates the whole of its 

 entire structure. Such a difference is, however, neither abso- 

 lute nor permanent. It is a temporary differentiation of pro- 

 toplasm into one of two different directions, and sooner or later 

 comes back to the original neutral or non-sexual state from 

 which it started, thus manifesting the phenomenon characteris- 

 tic of all protoplasmic irritability. 



Clark University, Worcester, Mass., May, 1892. 



