Experimental Evolution, Variation, and Heredity 105 



the female caused her to assume either the breeding plumage of the male or else 

 a modified type of male plumage. In chickens the removal of the testes from the 

 male resulted in a non-development of the comb and wattles, although the other sec- 

 ondary sextual characters were not altered. The removal of the ovary from the female 

 caused her to assume the secondary sexual characters of the male. The bearing of 

 these results upon problems of sex, heredity, and associated questions is discussed. 



No. 257. (Paper No. 28, Station for Experimental Evolution.) 



\YHITMAN, CHAFLES OTIS. Posthumous Works of, Edited by Oscar Riddle. 



Quarto. Published 1919. Price $30.00. 

 Some copies of volume III are for sale separately at $3.00. 



Vol. I. Orthogenetic Evolution in Pigeons. x+iQ4 pp., 88 pis., 36 text-fips. 

 Vol. II. Inheritance, Fertility, and the Dominance of Sex and Color in Hybrids 



of Wild Species of Pigeons. 224 pp., 39 pis., n text-figs. 

 Vol. III. The Behavior of Pigeons. Edited by H. A. Carr. xi+i6i pages. 



Most of the newer studies of heredity and evolution deal with the combination, 

 recombination, or segregation of characteristics in hybridization ; but usually the 

 past history or the sequence of origin of these characteristics of the organisms 

 studied is quite unknown. In this volume emphasis is placed on tracing the steps 

 by which the present plumage color-patterns have been reached in the numerous 

 species of Coltimbidae the pigeons. It was found that the original or ancestral 

 pigeon color-pattern is at the same time the ancestral pattern for birds in general; 

 and, further, that the principles of pattern modification, or evolution, found to 

 apply to the pigeons hold in other orders of birds as well. The material of chief 

 reliance in the present study is also a departure from that more commonly used 

 in studies of inheritance, in that it consists of pure wild species, and not of 

 domesticated and possibly mongrelized forms. The data strongly support the view 

 that the evolution of the characteristics of organisms is orthogenetic rather than 

 amphigenetic, and gradual rather than saltational. 



Knowledge of the present direction of evolution of certain characters made 

 it possible to learn that selection, in at least one group of characters, is successful 

 when the selection is made in the direction of evolution; it is unsuccessful when 

 it seeks to reverse the direction of evolution. Similarly, a knowledge of the 

 ancestral history of the plumage characters has made it possible to understand 

 the nature and meaning of certain "mutants," or marked color variants, which 

 appeared within the 17 years during which numerous wild species of pigeons were 

 bred in captivity. These "mutants" can be shown to be not wholly or really new. 

 The molts, or plumage changes, of pigeons offer special advantages for learning 

 the history of the individual plumage characteristics and for a study of the fact 

 of recapitulation. Certain experiments which were made in connection with the 

 molts confirm the view that recapitulation is the central fact of heredity. The 

 volume is well illustrated. 



Volume III of these studies (edited by H. A. Carr) primarily consists of a natural- 

 istic description and analysis of pigeon behavior. Nine chapters are devoted to the 

 reproductive cycle of activities, and one each to voice, homing, intelligence, and a 

 miscellaneous group of instinctive traits. The volume contains material of interest 

 to all students of animal behavior naturalists, physiologists, zoologists, and com- 

 parative psychologists. The author's motive in the collection of this material was 

 primarily biological, the attempt to study certain problems of evolution and inheri- 

 tance in the realm of behavior rather than of structure. In this sense the volume 

 may be regarded as a supplement of the previous ones. A broad basis was being 

 laid for a comparative study of pigeon behavior for the purpose of determining 

 species interrelationships. This phase of the work was far from complete. Many 

 instances of blending of behavior characteristics in hybridization are given. Further 

 evidence in support of orthogenesis is adduced ; this conception is applied to the 

 origin of intelligence and the instincts of incubation, tumbling, pouting, and homing. 



