DEPARTMENT OF EXPERIMKNTAL EVOLUTION. 79 



mine the degree to which their development is influenced by sex and in how 

 far they differ in reciprocal crosses. 



Heredity of Double Horn in Sheep. — A 4-horned ram presented by Mr. 

 Alexander Graham Bell was used for the first time, both with two 4-horned 

 ewes that he presented and also with other (even hornless) races. All males 

 and all females showed to a striking degree the influence of the double horn, 

 which appears to be dominant ; i. e., due to a special determiner. 



Independence of Soma and Germ-plasm. — During the year the Director 

 issued a paper entitled "The transplantation of ovaries in chickens." This 

 paper gives the details concerning six experiments in which the ovaries were 

 removed from each of two races of fowl and an exchange of the ovaries 

 made from the body of one to the other. In opposition to the conclusions of 

 Guthrie, it appeared first that the engrafted ovary did not enter into vital 

 connection with the tissues of the host, but on the contrary became encysted. 

 On the other hand, the tissue at the site of the removed ovary produced a 

 new ovary by regeneration. It was shown that Guthrie's results are capable 

 of the same interpretation. Therefore his results yielded no data as to the 

 effect of the soma on the germ-plasm. It is proposed to extend the experi- 

 ments with the aid of Mr. H. D. Goodale. 



Reciprocal Crosses in Relation to Sex. — A series of experiments has been 

 under way for several years on sex-limited characters in poultry. Some of 

 these bring a confirmation from the breeding side of current cytological 

 theories. Thus in a cross between a red-laced and a white-laced race, made 

 reciprocally, it appears that all sons, in whichever way the cross is made, are 

 white-laced, while daughters follow the sire in respect to the coloring of the 

 lacing. This would indicate that the odd, or sex-differentiating, chromosome 

 must, in poultry, be found in the female. Mr. H. D. Goodale, recently at- 

 tached to this station, is extending researches into this subject, using ducks 

 as well as fowl. 



HEREDITY OF EPILEPSY IN MAN. 



In connection with the Eugenics Record Office the Director cooperated 

 with Dr. David F. Weeks, of the New Jersey State Milage for Epileptics, 

 in the study of over 200 families with one or more epileptics as children. 

 The data concerning the families had been gathered with great care and at 

 much expense by the field workers of the Eugenics Record Office and the 

 State of New Jersey. Their studies of the product of certain selected human 

 matings have much the value of experimental data. It appeared from this 

 study that epilepsy behaves in inheritance as though it were due to the ab- 

 sence of some unit-character that makes for neural strength, and is an 

 equivalent in inheritance of "feeble-mindedness." Thus if both parents are 

 without the character that makes for neural strength, all of the children lack 

 it; and if both parents, though neurally strong themselves, belong to weak 



