346 EVOLUTION, GENETICS, AND EUGENICS 



in the degree of perfection of adaptation in these two widely different 

 species, each highly successful in its own milieu and each cosmopolitan 

 in distribution. In view of such considerations as these, it is not easy 

 to maintain that evolution is a process of becoming better and better 

 adapted. 



Specialization. — Various other criteria of progress have been sug- 

 gested. One of these is specialization. Are the most highly special- 

 ized organisms more advanced than the less specialized? Are the 

 more specialized ones closer to the ultimate ideal goal of evolution than 

 the more generalized? Now, many of the most intensely specialized 

 types of organisms are the parasites that have, in many cases, under- 

 gone degeneration of sense organs, locomotor structures, and even 

 digestive systems, but have developed specialized structures making it 

 possible for them to live and thrive in some particular system of some 

 species of host animal. Here is specialization carried to extremes, but 

 is it progress? I believe it is, and for the following reasons: 



A primary objective of living organisms is that of exploiting to the 

 fullest possible extent the energy resources of the world. Ultimate 

 success will be attained only when no further energy resources remain 

 to be exploited. Now the sources of energy are many and varied, and 

 each different energy source requires a different type of energy-exploit- 

 ing equipment. Progress in specialization would therefore involve the 

 evolution of as many highly specialized types of organisms as there are 

 highly specialized energy sources. Thus there is a very real value for 

 life as a whole in the production of numerous highly specialized forms, 

 even though some be, from the morphological viewpoint, degenerate 

 and degraded parasites. 



Another type of specialization that has had a long and steady pro- 

 gressive evolution is the specialization of parts of the single organism 

 for the performance of varied bodily functions. This type of speciali- 

 zation is commonly called "division of labor." In the course of animal 

 evolution this specialization of parts begins at the lowest level in the 

 Protozoa, where portions of the protoplasm are specialized to form 

 organelles of various kinds, each kind performing its own special func- 

 tion. Among the lower Metazoa, such as Coelenterata and Platyhel- 

 minthes, we have a new level of organization, built up of aggregates 

 of units, each equivalent, in a sense, to a whole protozoan individual. 

 In these multicellular individuals division of labor is accomplished by 

 specializing the cell units for different functions, with a corresponding 

 increase in general efficiency of the individual. 



