342 



SCIENCE 



[N. S. Vol. LIII. No. 1371 



so far as Y is concerned is exactly tlie condi- 

 tion demanded in the poultry type of sex- 

 linked inheritance for a carrier of sex-linked 

 characters. This line of thought leads to the 

 following hypothetical outline of the evolu- 

 tion of sex-linked inheritance. 



1. Sex-linked inheritance begins with the 

 inclusion in the nucleus of the egg of a struc- 

 ture, X, perhaps originally found in the cyto- 

 plasm and handed on there from egg to egg in 

 the female line, never in the male line. This 

 structure is itself (or is attached to) the spe- 

 cific determiner of f emaleness ; it is an element 

 which keeps the organism at the metabolic 

 level of femaleness, its absence allowing the 

 organism to drop down to the metabolic level 

 of maleness. Characters (genes) located in 

 5 would pass only from mother to daughter. 



2. From the foregoing state two divergent 

 lines of evolution may have arisen. 



(a) In one the X chromosome becomes 

 duplicated in the female (perhaps by split- 

 ting at the reduction division) and is in con- 

 sequence found in all eggs after maturation. 

 It thus passes into male zygotes as well as 

 female zygotes. The female will now be XX 

 in formula, the male XO. Whatever inherited 

 characters have their genes located in the X 

 chromosome will now be transmitted as in 

 Vrosophila and man. 



(6) A chromosome, T, not concerned pri- 

 marily in sex-determination, may develop as 

 the synaptic mate of X in the egg; it would 

 at once pass into male offspring and being 

 transmitted in sperm cells would speedily 

 produce the male type T-Y. But in the 

 female, Y would be kept from becoming 

 duplex by the presence of X, the synaptic 

 mate of Y. If Y contained genes, these 

 would be transmitted as are the genes of sex- 

 linked characters in poultry and other birds 

 and in moths. 



3. If in the Drosophila type of inheritance, 

 Y should come to contain genes, these would 

 be handed on from father to son, without ever 

 entering a female zygote (.Lehistes type). In 

 the poultry type of sex-linked inheritance, Y 

 would not afford a suitable mechanism for 

 this one-sided type of inheritance, since Y 



there passes into females. Hence the Lebistes 

 type must be a further evolution of the Droso- 

 phila and human type, not of the poultry type. 

 W. E. Castle 

 BussEY Institution, 

 March 1, 1921 



THE AMERICAN ASSOCIATION FOR 

 THE ADVANCEMENT OF SCIENCE 



SECTION A AND ASSOCIATED MATHEMATICAL 

 ORGANIZATIONS 



Section A of the American Association for the 

 Advancement of Science met in Chicago on Wed- 

 nesday morningj December 29, in joint session 

 with the American Mathematical Society (Chicago 

 Section), the Maithematical Assooiatiou of Amer- 

 ica, and a group of persons interested in the His- 

 tory of Science.i Professor D. R. Ourtiss, chair- 

 man of the Section, presided. Professor O. D. 

 Kellogg, of Harvard University, the retiring chair- 

 man, gave an address entitled ' ' A decade of Amer- 

 ican mathematics." Professor Florian Cajori 

 gave an illustrated address on "The evolution of 

 algebraic notations." This meeting was attended 

 by more than 200 persons, including 80 members 

 of the American Mathematical Society and 150 

 members' of the Mathematical Association of 

 America. 



At the business meeting following the program, 

 the nominations made by the sectional committee 

 (on December 27) were approved. These nomina- 

 tions, which were acted upon by the council of the 

 association at its meeiting of December 31st, were 

 as follows: 

 I. For Chairman of the Section, who will pre- 

 side at Toronto and give his retiring ad- 

 dress at Boston, Oswald Veblen, Princeton 

 University. 

 II. For Secretary of the Section, who will hold 

 office until the meeting of 1924-25, William 

 H. Boever, Washington University. 

 According to the new constitution four instead 

 of five members, in addition to the chairman and 

 secretary, constitute the Sectional Committee. 

 Therefore it was unnecessary to elect a member to 

 succeed Professor H. L. Eietz, whose term expired 

 with the Chicago meeting. The four members are : 

 Dunham Jackson (January, 1920, to December, 

 1924), Minneiapolis, Minn.; A. D. Pitcher (Jan- 

 uary, 1920, to Decemher, 1923), Cleveland, Ohio; 

 Gilbert A. Bliss (January, 1920, to December, 

 1922), Chicago, Illinois; James M. Pag« (January, 

 1 Science, February 18, 1921 (p. 164). 



