February 7, 1919J 



SCIENCE 



149 



The greatest service of this method appears 

 when the two sets of allelomorphs are com- 

 bined. The student has learned to multiply 

 a- + 2ab -\~b- by the expression .v= + 2xy + y-. 

 He will iKjrform the operation as one familiar 

 to him and he can readily be taught to recog- 

 nize the four pure strains a-x-, ofiy-, h-x", i-y-. 

 Suppose a and y represent the dominant char- 

 acters and b and x represent the recessives, 

 emphasizing the fact that the dominant is 

 effective whether appearing as the first or as 

 the second ixiwer. Supiwse a represent tall- 

 ness and y represent red flower in a plant. 

 Gathering the results of the multiplication 

 according to visible attributes we have four 

 columns representing the Mendelian ratio 

 9:3:3:1. 



This is only one of many devices all alike 

 fundamentally but it has the great value of 

 utilizing a familiar process. Many times I 

 have seen it clear up a badly fogged situation. 

 It is worth trying on the discouraged jjupil at 

 any rate. Love Holmes Miller 



State Normal School, 

 Los Angeles, Caltf. 



SILEXITE: A NEW ROCK NAME 



In the granites of the Adirondack region the 

 writer has observed many bodies of pure or 

 nearly pure silica of igneous origin in the form 

 of dikes segregation masses practically in situ, 

 or inclusions. Among many other districts 

 where similar masses of silica occur is the 

 Silver Peak quadrangle of Nevada in an ac- 

 count of which Spurr has described many con- 

 siderable bodies of quartz of magmatic origin. 

 Numerous fine examples of so-called "quartz 

 dikes " occur in the Holyoke quadrangle of 

 western Massachusetts described by Emerson. 

 The need for a definite name to apply to any 



such body of silica has impressed itself upon 

 the writer during the preparation of a dis- 

 cussion of the acidic dikes of northern New 

 York. Such terms as " quartz dikes " or " dike 

 quartz " are not comprehensive enough, first, 

 because much of the silica under consideration 

 is not in dike form, and, second, because the 

 silica may be either quartz or tridymite de- 

 pending upon the temperature of crystalliza- 

 tion. 



The term " selexite " is proijosed for any 

 body of pure or nearly pure silica of igneous 

 or aqueo-igneous origin which occurs as a dike, 

 segregation mass, or inclusion within or with- 

 out its parent rock. This term is based upon 

 the name " silex " used by Pliny in his 

 " Natural History " for the mineral now known 

 as quartz. '' Silexite," therefore, not only has 

 the advantage of simplicity as a name, but also 

 it directly suggests the composition of the 

 rock which it names. 



William J. Miller 



Smith College 



THE WESTERN SOCIETY OF 

 NATURALISTS 



The Bay Section of the society held a two-day 

 meeting at Stanford University, November 29-30, 

 1918. The sessions, held in Jordan Hall, were well 

 attended and the various papers which were of 

 more than usual interest were enthusiastically re- 

 ceived. Dr. Joseph Grinnell served as chairman. 

 An informal dinner Friday evening and a field trip 

 on Saturday afternoon were features of the occa- 

 sion. Dr. S. D. Townley gave the evening lecture 

 on ' ' The recent solar eclipse. ' ' 



The following papers were presented: 



Isolation as a factor in species forming: David 



Starr Jordan, Stanford University. 

 A Thanksgiving Day registration of plants in 



bloom on Mt. Tamalpais: Alice Eastwood, 



California Academy of Sciences. 

 Use of selective dyes in sanitary examination of 



water: Ivan C. Hall, University of Calif ornia. 

 The naturalist's place in his community: E. W. 



Allen, Fresno High School. 

 Adaptation of the eyes of birds for rapid flight: 



J. R. Slonaker, Stanford University. 

 Intrauterine absorption of conceptsuaes : A. W. 



Meter, Stanford University. 



