edpartme;nt of experimental evolution. 87 



By Dr. Lutz: The tegminal position in Gryllus. Inheritance of variations in the 

 color pattern of Crioceris. Variation and correlation of characters of Gryllus. 

 Inheritance of the manner of clasping the hands. Combination of alternative 

 and blending inheritance. 



By Mr. R. H. Johnson : Evolution in the lady-bird beetles. 



In addition, our associate, Dr. W. E. Castle, at Harvard University, has 



published alone or with students papers on results of investigations on — 



Heredity of coat characters in guinea-pigs and rabbits. Heredity of hair-length 

 in guinea-pigs, and its bearing on the theory of pure gametes. Color varieties 

 of the rabbit and other rodents, their origin and inheritance. Reversion in- 

 duced by cross-breeding and fixation. Selection and cross-breeding in relation 

 to the inheritance of coat-pigments and coat-patterns in rats and guinea-pigs. 

 Studies in inheritance in ear-size, weight, skeletal dimensions, and color of 

 rabbits. 



It is impossible to state in a few words the chief results of these varied 

 contributions. In the main they have demonstrated the wide application of 

 the Mendelian principles of inheritance to the characteristics of animals and 

 plants, both domesticated and feral. They have silenced the objection that 

 the Mendelian phenomena related only to "artificial" varieties and proved 

 that they hold equally for species in nature. They have thoroughly analyzed, 

 for the first time, the phenomena of dominance in transmission, and have 

 shown its wide fluctuation from perfection to an impotency such that appar- 

 ently there is no transmission. They have introduced the idea of the domi- 

 nance of the more-developed characteristics over the less-developed, and have 

 extended the ideas that while the absence of a characteristic is recessive to 

 presence, the characteristic itself may be an inhibiting factor. They have 

 shown the composition of many color-characteristics out of several factors, 

 revealing a hitherto unsuspected complexity of the germ-plasm. They have, 

 on the other hand, dealt with certain cases, particularly in insects and Oeno- 

 theras, where segregation of characters seems not to occur. 



Finally, this Station has collected and begun to publish studies on data 

 relating to inheritance of human qualities. Eye-color, hair-color, and hair- 

 form have been by us first demonstrated to behave in Mendelian fashion and 

 to be predictable in the offspring. In cooperation with the Committee of 

 Eugenics of the American Breeders' Association the work of gathering data 

 concerning the transmission of human characteristics goes on apace. 



Studies have been undertaken on the mechanism of heredity, which is cur- 

 rently thought to reside in the stainable bodies (chromosomes) of the germ- 

 cells. Miss Lutz has organized a series of critical studies which will, it is 

 expected, answer definitely the question whether the determiners of char- 

 acteristics are carried exclusively in the chromosomes, 



THE MODIFICATION OF CHARACTERISTICS. 



By changed environmental conditions characteristics may, of course, be 

 changed and the modifications, though usually somatic only, are sometimes 

 transmissible (Tower). By selective breeding, characteristics may be modi- 



