122 CARNEGIE INSTITUTION OF WASHINGTON. 



found 3 which showed white flecks and 1 which showed a dark yellow fleck 

 which was presumably homozygous for yellow. The evidence seems con- 

 clusive, therefore, that the somatic mutations occur in both directions, to 

 dominants and to recessives. It is impossible to give reliable figures for the 

 relative frequency of mutation in the two directions, since, although yellow 

 flecking on whites seems relatively common (89 yellow-flecked flowers out of 

 over 2,500 examined), white flecks on yellows are less readily discernible." 



Sap Properties of Egyptian and Upland Cotton and of their Fi Hybrids. 



Preliminary observations at Sacaton, Arizona, in 1920 indicated that 

 Egyptian and Upland cotton differ in their sap properties (Year Book, 

 Carnegie Inst. Wash. 1920, p. 143). Careful plantings were made 

 at the Cooperative Testing Station at Sacaton, through the courtesy 

 of Dr. T. H. Kearney, for the purpose of a more exact comparison of 

 Meade and Acala Upland Cotton with Pima Egyptian cotton, and of 

 the Fi hybrid between Pima and Meade with the two parent species. 

 The work on the sap properties of these four series of plants occupied 

 the attention of Dr. Harris, with the assistance of J. V. Lawrence, W. F. 

 Hoffman, A. T. Valentine, and Mrs. J. V. Lawrence during the month 

 of August. 



Susceptibility to Inoculable Cancer. 



Heredity of susceptibility. — In the last annual report, evidence was 

 offered by Dr. Little to show that in all probability from three to five 

 Mendelizing factors were involved in determining the susceptibility 

 and non-susceptibility of hybrids between Japanese mice and albinos 

 to a sarcoma J. W. B. of the Japanese mice. 



During the past year adeno-carcinomas dbrA and dbrB have both 

 been used by him in a series of genetic experiments involving a cross 

 between the susceptible dilute brown race and a non-susceptible 

 albino race. Both parent races were inbred — the dilute brown race 

 especially so. Fi hybrids between dilute brown and albinos grew 

 both the A and the B tumors in every case. The tumors were implanted 

 subcutaneously on the opposite sides (axillary regions) of the animals 

 used. The result given by the Fi mice was expected and predicted, 

 since the degree of inbreeding of the dilute brown race was so great 

 that the gametes contributed by various individuals from it to the Fi 

 hybrids were essentially alike. They each presumably contained in a 

 simplex condition the genetic factors which together form the "dilute 

 brown" complex and which, therefore, bring about the favorable treat- 

 ment of implants of the dbrA and dbrB tumors. 



In the experiments involving the Japanese mice and albinos, the 

 parent stocks were so widely divergent from one another biologically 

 that it is not at all surprising that the number of Mendelian factors 

 underlying the difference was found to be large. (In the case of the 

 epithelial tumor, carcinoma J. W. A., it was estimated at 12 to 14.) 



