ABSTRACT. ^^^>^. 



The object of this investigation was mainly twofold: First, to de- 

 termine the mode of evolution of the various lines of a great network 

 with reference to traits which have direct bearing on social efficiency; 

 second, to study the variation in the grade of these traits and the re- 

 lation of this variation to the types of mating. An answer was sought 

 to the following questions : By what process does marked defect, such 

 as lack of number-sense, or aggressiveness, disappear from some lines 

 and persist in others? What measure of improvement is directly 

 effected through selected matings? The data collected were further 

 used to draw conclusions concerning comparative fecundity, compara- 

 tive survival, differential migration, and various contentions of our 

 immigration problem, and, finally, our conclusions were considered in 

 their bearings on the present-day program for race betterment. The 

 study comprises 1,822 individuals, nearly half of whom are in the 

 direct line of descent from two pairs of German immigrants of more 

 than a century ago. The remainder were considered in connection 

 with the strains into which the descendants of these couples married. 

 The research began with 4 young people, patients at the Institution 

 for the Feeble-Minded of Western Pennsylvania, at Polk, Pennsyl- 

 vania. When the wide variability of the material with reference to 

 socially efficient traits became apparent, the study was extended to 

 all so-called normal lines of the two networks, and a further attempt 

 made to grade the individuals in calculating ability, aggressiveness, 

 and perseverance. 



The first network, comprising lines A to E, was founded by an honest, 

 aggressive, plucky, persevering, far-sighted man and his amiable easy- 

 going wife, who was totally lacking in sense of number and proportion. 

 This network breaks up into widely divergent lines. 



Line A, founded by the slow, stupid, non-aggressive, but persevering 

 eldest son and an irritable, sexually immoral wife of average mentality, 

 increases its aggressiveness, perseverance, and calculating ability by 

 marriage into stocks showing these traits. The condition of all rep- 

 resentatives of these lines, with one exception, is average or above the 

 average with reference to these traits. The exception is furnished 

 by a marriage into a degenerate line of the same network. 



Line B was founded by a non-aggressive, non-persevering son with 

 some calculating ability. His wife was able, but sexually lax. Their 

 only child, a daughter, appears to have escaped the serious defects of 

 both parents and has founded a line showing fair aggressiveness, per- 

 severance, and calculating ability. Sex morality is characteristic of 

 this line. 



