104 Experimental Evolution, Variation, and Heredity 



No. 296. (Paper No. 32, Station for Experimental Evolution.) 



KEY, WILHELMINE E. Dissimilar Heredity and Social Fitness as illustrated in a 

 Certain Pennsylvania Family. In press. 



This is a study of nearly 2,000 individuals comprising six generations, derived 

 from immigrant ancestors of over a century ago. The networks show an evo- 

 lution of lines widely divergent with reference to such traits as calculating ability, 

 aggressiveness, and perseverance. Marriage of individuals possessing a low or 

 medium grade of these traits into stocks having a higher grade has resulted in 

 improvement in later generations ; marriage into stocks having a low grade of 

 these traits has brought about persistence of the defective condition. In one line 

 a condition of mental retardation in earlier generations is being replaced by a 

 more rapid rate of development, and here there has been marriage into stocks 

 showing a normal rate of mental development. 



All lines, socially fit as well as unfit, show marked decrease in fecundity, 

 while for the socially fit lines the survival ratios are increasing. The normally 

 endowed tend to push out into new sections of country, leaving the slower and 

 more dependent to mate with their kind and to found families to be supported 

 at public expense. The failure of the degenerate branches to react favorably 

 to an improved social environment would indicate low efficiency due primarily 

 to native incapacity, which in its turn is traceable to the mating of defect with 

 defect. Amalgamation and assimilation have been complete and have here con- 

 sisted in the marriage of individuals of high mental potentiality into the better 

 native stocks and the adoption of their standards, while the marriage of individ- 

 uals of low mental potentiality into inferior stocks has brought about a diversity 

 of degenerate condition with correspondingly low standards of living and attain- 

 ment. The whole history points to the necessity of more careful study of im- 

 migrant stocks and the control of marriages that threaten to perpetuate socially 

 unfit strains. 



No. 241. (Paper No. 26, Station for Experimental Evolution.) 



CASTLE, W. E., and S. G. WRIGHT. Studies of Inheritance in Guinea-Pigs and Rats. 

 Octavo, 192 pages, 7 plates, 7 text figures. Published 1916. Price $2.50. 



An Expedition to the Home of the Guinea-Pig and some Breeding Experiment* 



with Material there obtained. By W. E. CASTLE. Pages i to 55. 

 An Intensive Study of the Inheritance of Color and of Coat Characters in Guinea- 



Pigs, with especial reference to Graded Variations. By SEWALL G. WKIGHT. 



Pages 57 to 160. 

 Further Studies of PiebId Rats and Selection, with obserrations on Gametic 



Coupling. By W. E. CASTLE. Pages 161 to 192. 



This paper contains an account of the life-history of a small species of cavy 

 (supposed to be the ancestor of domesticated guinea-pigs) found in the vicinity of 

 Arequipa, Peru, together with an account of hybridization experiments between 

 this and other races of cavy obtained in the same general region. The growth 

 rates of different races are compared, and it is found that they involve complete 

 blending as regards size inheritance, with a physiological increase of size in Fl 

 not due to heredity and which accordingly does not persist beyond the F j genera- 

 tion. Inheritance formula are worked out for the various characters studied 

 and an analysis is made of cases involving multiple allelomorphs as well as sup- 

 plementary and modifying factors. 



No. 243. (Paper No. 27, Station for Experimental Evolution.) 



GOODALE, H. D. Gonadectomy in Relation to the Secondary Sexual Characters of 

 Some Domestic Birds. Octavo, 52 pages, 7 plates. Published 1916. 

 Price $1.50. 



This book describes the effects of ablation of the primary sexual organs upon 

 the secondary sexual characters of two species of domestic fowl, viz., ducks and 

 chickens. In ducks the complete removal of the testes caused the male to remain 

 in the breeding plumage the year round, while the removal of the ovary frorc 



