868 EXPEKIMENT STATION RECORD. [Vol. 37 



acres in crops per horse, while on the small farms there were but 16.8 acres 

 per horse. Similar results were found on both the Ohio and the New York 

 farms, though in these States the difference between the two groups was not as 

 great as in Illinois. 



Some important essentials in profitable horse production, C. W. McCamp- 

 BELL {Eayisas Sta. Insp. Circ. 2 {1916), pp. S). — In addition to brief notes on 

 profitable horse production, a list is given of stallions licensed in Allen County 

 during the year ended October 1, 1916. Similar lists are published for all the 

 other counties of the State, each list being issued as Inspection Circular 2. 



The theory of sex as stated in terms of results of studies on tlie pigeon, 

 O. Riddle {Abs. m Anat. Rec, 11 {1911), Xo. 6, p. 510). — Studies on sex control 

 in pigeons have indicated the nature of the initial difference between germs of 

 prospectively different sex-value. " This difference rests upon different levels of 

 metabolism, and when the metabolic level of a given germ is shifted from the 

 level characteristic of the germ of one sex sufficiently toward the level of the 

 other sex, it develop.s into an organism of the sex which corresponds to the 

 acquired, or later, level. The initial difference characteristic of the tvro kinds 

 of (sex) germs, tends to persist and characterize the adults of the two sexes. 



" Sex is based on a quantitative difference. Intermediates of the normal ex- 

 tremes have been experimentally produced, and the normal extremes have them- 

 selves been experimentally accentuated." 



Factors influencing the sex ratio in the domestic fowl, R. Feakl (Science, 

 n. ser., 46 {1917), No. 118S, p. 220). — In this paper on the sex production ques- 

 tion in the common fowl, results are given of eight years' experimentation at the 

 Maine Station in which over 22,(X)0 Individuals were Involved. 



This work indicates first that the determination of sex in poultry is primarily 

 a matter of a definite, hereditary mechanism, just as it is in insects and other 

 forms which have been studied. At the same time, it is demonstrated that under 

 certain physiological circumstances the operation of this mechanism may be 

 modified in such a way as to lead to the production of more females in propor- 

 tion to the number of males. The chief factor in bringing about the modification 

 in the direction of u larger production of females is the fecundity or laying 

 ability of the hens used as breeders. The larger the number of eggs which a hen 

 lays before being put into the breeding pen. the larger will be the proportion of 

 females and the smaller the proportion of males produced by her eggs. 



Crossing over in the sex chromosome of the male fowl, H. D. Goodalk 

 {Science, n. ser., 46 {1917), A'o. 118S, p. 21S). — In studying sex linkage in 

 fowls, crossing over in the sex chromosomes of the male was seen to have 

 occurred. This preliminary report deals only with the factors themselves, with- 

 out regard to the somatic appearances of the individuals. "Three dominant 

 sex-linked characters, namely, B, I, and S, were employed. B and I were intro- 

 duced on one side, S on the other. Hence the Fi males were all BI, S ; B and I 

 being in paternal (or maternal) sex chromosome, S in the maternal (or pater- 

 nal). These males have been tested by mating them back to females of the 

 composition b Is, b is. 



" If there were no crossing over, offspring of this back cross showing the com- 

 bination of somatic characters found in the Fi male would not occur. Actually, 

 however, they do occur, thus demonstrating that crossing over has occurred, a 

 chromosome having the composition BIS having been formed. Other cross over 

 classes have appeared, but the one cited is the one at the present age of the 

 chicks most easily recognized." 



Further data on the relation between the gonads and the soma of some 

 domestic birds, H. D. Goodai.e (.16.«. in ArnJt. Rec. 11 {1917), Xo. 6, pp. 512- 

 514). — Published data on the ablation of the testes and ovaries of domestic 



