THE BASIS OF SOCIALITY 253 



generally useful because it accomplishes something new, something 

 which the homogeneous mass could not do before the variation 

 occurred. Progress is generally such differential interstitial growth. 



Differentiation, however, is not invariably the open sesame to 

 success. The secret of success lies in the degree of adaptation, and 

 success, it may again be repeated, must be interpreted in terms of 

 survival. We commonly say that when certain plants are trans- 

 ferred northward they tend to degenerate by becoming dwarfed and 

 by losing some of their highly developed specialties. They have a 

 tendency, like old varieties of plants, to assume some primitive or 

 inferior type. Degeneracy or deterioration is, however, a relative 

 term, return to a simpler form, i. e., a decrease in the differentiation 

 of the plant, being often the successful means employed to secure a 

 further lease of life. In the same way with human beings, poverty 

 often places an embargo on differentiation. The highly developed 

 individual, stricken with poverty, must needs forego the satisfaction 

 of many tastes, and revert to a more common and primitive type. 



The utility of differentiation is, however, manifest on all sides. 

 Death entered into the world with all its blessings, the old undying 

 types giving place to the possibility of an ever-increasing variation. 

 Sex entered, according to Weismann, and increased the number of 

 combinations and variations. Plants become annuals and biennials 

 from a perennial condition. Changes in the plant and animal 

 world meet the changes of the seasons, the temperature, the food 

 supply, and the changing demands of the rest of the plant and 

 animal world. Bailey suggestively remarks that the development of 

 life took two divergent lines — that of the circular arrangement of 

 parts and that of bilateralism. The first line, developing in obedience 

 to a peripheral or rotate type of organization, ends in the echinoderms 

 and some of the moUusks. This type reached its zenith and, accord- 

 ing to Cope, has left no line of descent. The progressive and reg- 

 nant type of animal life appeared in the vermes, or true worms, 

 forms which are characterized by a two-sided or bilateral, and there- 

 fore more or less longitudinal, structure. By this means greater 

 differentiation was made possible. A cephalic or head-forming 



