288 GENERAL REMARKS. 



continuous progressive specialization to more and 

 more differentiated structure with correspondingly 

 increased functional powers, or larger or different 

 fields of work. At other times it may lead us in a 

 wave line, which follows a devious course, rising part 

 of the time through progressive specialization, and then 

 falling for another period of time through specializa- 

 tion by reduction. If the animals under consideration 

 be parasites, they may continue on this descending 

 plane both in the growth of the individual and the 

 evolution of the group. Nevertheless the resulting 

 adult is not necessarily of " low grade " in any scien- 

 tific scheme of arrangement founded upon the princi- 

 ples of evolution. It is, however, farther removed 

 ft-om the primitive type, and is extremely specialized. 

 The use of the aesthetic terms " low " and " high " 

 have come from a period in the history of our science 

 when nature was made to assume a rigidly progressive 

 aspect, each division of the animal kingdom represent- 

 ing a finger-post pointing towards the so-called perfect 

 animal, man, each rising higher and higher in the 

 scale of perfection whose standard was the human 

 organization. Such artificial ideas revenge themselves, 

 and words become their ready instruments, first to 

 express what is false, and then to help in binding the 

 mind with the conservative fetters of habit. 



