468 



SCIENCE 



[N. S. Vol. LI. No. 1323 



are to be still considered as possibilities, 

 tbough not probabilities. The six and seven 

 factor hypotheses appear to be definitely elim- 

 inated. 



The non-susceptible back cross animals 

 which should by the multiple factor hypothesis 

 contain in many cases part, but not all, of the 

 factors for susceptibility are being tested by 

 breeding back with the F^ animals. If four 

 factors are involved, as seems likely, of every 

 fifteen such back cross animals approximately 

 four or 26.6 per cent, should have three; six 

 or 40 per cent, two; four or 26.6 per cent, 

 one; and one or 6.6 per cent, none of the four 

 factors necessary for continued growth of the 

 tumor. When crossed with F^ animals these 

 back cross types should give the following 

 ratios of susceptible to non-susceptible ani- 

 mals in their progeny. 



Ratio of Susceptible 

 to Non-Suaceptlbl« 

 Type ot Back Cross Progeny 



Having three factors 1 : 3.7 



' ' two factors 1 : 6.1 



' ' one factor 1 : 9.7 



' ' zero factors 1:15 



The first two categories should be easily 

 recognizable and together form 66.7 per cent, 

 of the back cross animals. Such tests have 

 now been begun. 



The sex chromosome has been eliminated 

 as a probable carrier of any of the four fac- 

 tors as follows. If mice like other manunals 

 have the female XX and the male XY in 

 formula, the use of susceptible Japanese 

 waltzing males to form the F^ animals used, 

 gives daughters carrying his X, and sons his 

 T chromosome. If now 'his sotis only are 

 used to produce the back cross generation by 

 mating with common non-susceptible females, 

 all the X chromosomes in the resulting 

 animals will be derived from common non- 

 susceptible mice. Unless therefore, crossing 

 over between the X and Y chromosomes occurs 

 frequently, any susceptibility factor borne in 

 the X chromosomes of the original Japanese 

 waltzing males used, has been eliminated. 



While further investigations are in prog- 

 ress, we may conclude provisionally that: 



1. From three to five factors — i^robably 



four — are involved in determining suscepti- 

 bility to the mouse sarcoma J. W. B. 



2. That for susceptibility the simultaneous 

 presence of these factors is necessary. 



3. That none of these factors is carried in 

 the sex (X) chromosome. 



4. That these factors Mendelize independ- 

 ently of one another. 0. C. Little 



THE AMERICAN ASSOCIATION OF PE- 

 TROLEUM GEOLOGISTS 



The fifth annual meeting of the American Asso- 

 ciation of Petroleum Geologists was held in Dallas, 

 Texas, March 18 to 20, with headquarters at the 

 Adolphus Hotel. The annual meeting of 1919 also 

 was held there, and Dallas was selected for a sec- 

 ond time 'because of its accessibility to the south- 

 western oil fields, where large numbers of mem- 

 bers are now working. Almost three hundred 

 members and more than a hundred visitors were 

 registered from all parts of the "United Staites. 

 The association was honored by the presence of 

 Dr. George Obis Smith, director of the United 

 States Geological Survey, who was made an honor- 

 ary member of the association. Other distin- 

 guished members present from a distance were E. 

 P. McLaughlin, oil and gas inspector of California; 

 Dr. Ralph Arnold, consulting geologist, of San 

 Francisco, New York and London; Professor Bos- 

 well H. Johnson, of Pittstourgh; and Everett De- 

 Golyer and Donald F. McDonald, of New York. 



The opening session was called to order by 

 President I. C, White, state geologist of West 

 Virginia, well known as the father of the anti- 

 clinal theory. Greetings were given by a repre- 

 sentative of the Oil Development Committee of the 

 Chamber of Commerce of Dallas, and by Robert 

 H. Hill, president of the Southwestern Geological 

 Society, and responded to by President White. 



The general subject of this session was New 

 Mexico and Northwestern Texas. Papers were 

 given by Dr. John K. Knox, on "The geology of 

 New Mexico as an index of probable oil re- 

 sources," by Dan L. Garrett on "The s^trati- 

 graphy of northeastern New Mexico"; by Wal- 

 lace G. Matteson on the "Oil possibilities of north- 

 eastern New Mexico," and by Dr. Chas. N. Gould 

 on "Types of structure at Amarillo, Texas." 



The Thursday afternoon session was devoted to 

 a consideration of the Louisiana and Texas fields, 

 and papers were given by Chester A. Hammill on 

 "The structure of northwest Louisiana"; by Sid- 



