August 25, 1905.] 



SCIENCE. 



249 



apparatus and method, exhibiting Ewing's 

 experiment for demonstrating Weber's molecu- 

 lar theory of magnetism, and showing the 

 magnetic field by use of iron filings. The 

 apparatus, which was very simple, is described 

 as follows : The object to be exhibited is 

 placed on a base (which in the speaker's 

 apparatus consisted of a 60 by Y5 centimeter 

 drawing-board covered wfth white paper). 

 Against two nails driven into this base near 

 the back a large plane mirror is placed, and 

 inclined forward at any desired angle by 

 means of a wire attached to the top of the 

 mirror and passing through a binding post 

 screwed into the back of the base. To each 

 upper corner of the mirror is clamped a 50- 

 candle-power General Electrical Company 

 ' stereopticon ' lamp protected in front by 

 metal half shades. These brilliantly illumin- 

 ate the object and obviate shadows. The 

 apparatus can, of course, be made permanent 

 by hinging the mirror to the ba-se and fasten- 

 ing the lights permanently. It will be seen 

 that the apparatus has many applications in 

 the teaching of the biological as well as phys- 

 ical sciences in exhibiting objects that can 

 not be turned on their edge. The apparatus 

 has the advantage over the projecting lantern 

 with horizontal attachment, first that it does 

 not require a darkened room; second, opaque 

 objects can be exhibited; third, the size of 

 the object to be exhibited is limited only by 

 the size of the mirror; fourth, the apparatus 

 is not only easy to operate, but can be put 

 together from materials usually found in any 

 laboratory. 



At the close of the regular meeting, the 

 annual business meeting was held. The an- 

 nual report of the secretary was received. 

 The following oflficers were elected for the 

 ensuing year: 



President — Professor F. S. Shiver. 

 Vice-President — Professor S. W. Reaves. 

 Secret cu-y — Dr. F. H. H. Calhoun. 

 Memhers of Council — Dr. J. H. James and Pro- 

 fessor F. T. Dargan. 



Haven Metcalf, 



Secretary. 



SPECIAL ARTICLES. 



ASSORTATIVE MATING IN MAN. 



As was pointed out in Biometriha, Vol. II., 

 No. 4, 1903, " Darwin has given the name of 

 sexual selection to the general conception of 

 differential mating. As opposed to iDure 

 random mating within the population, we 

 have first preferential mating, in which male 

 or female classes with certain values of a 

 character find it less easy to mate than other 

 classes with different values. Secondly, we 

 have assortative mating, in which, while all 

 classes of males and females find mates, cer- 

 tain classes of males appear to be attracted to 

 certain classes of females. If the male class 

 of a given character tends to mate with a 

 female class with generally like character we 

 have a tendency to homogamy. Homogamy 

 as one type of assortative mating is simply 

 measured by the correlation between the two 

 characters in the male and female of the pair. 

 The infliience of homogamy on the character 

 of successive generations of a population may 

 be very great indeed, and the whole range of 

 effect from pure random matings to perfectly 

 homogamous unions within a population is 

 almost but not quite as important as the dif- 

 ference between self and cross fertilization in 

 plants. It has the distinctive features as 

 compared with self fertilization, that (1) it 

 may have any degree of intensity, (2) it may 

 be confined to special characters, and (3) it 

 is not complicated by any of the supposed 

 harmful effects of inbreeding." 



In the paper from which the paragraph I 

 have just quoted was taken we dealt with 

 assortative mating in man with respect to a 

 character — longevity — concerning which there 

 could not possibly be any conscious selection. 

 The characters dealt with by Pearson in for- 

 mer papers^ are also — at least, probably — not 

 made the object of conscious selection. The 

 coefficients of correlation between man and 

 wife in all these cases average about .2 — or 

 ' husband and wife are as much alike as uncle 

 and niece, and probably as much alike as, if 

 not more alike than, first cousins.' 



^Phil. Trans., Vol. 187, A, p. 273, and Vol. 195, 

 A, p. US; Biometrika, II., p. 353. 



