LINNEAN SOCIETY OF LONDON. 25 



side of two and the right side of four females, and in a smaller 

 degree in other males and females. In one male with all the 

 spots small, tliat in the left fore-wing cell is barely visible, 

 although the right is the largest spot in the entire pattern of the 

 specimen. 



Mr. Bacot bred from the male first described aud a feiiiale 

 which is either lost or at any rate cannot now be identified with 

 certainty. From these parents he reared in 1901 a family of 

 b males and 5 females. In three males the spot is large and 

 normal on both sides, in one it is very small on the right, in 

 one very small and divided into two on both sides. The left 

 spots of the remaining three males resemble the male parent in 

 varying degrees : in one it bears a minute central dark spot, 

 in one (A) it resembles the male parent but with a rather smaller 

 invasion, in the third the invasion is much larger leaving only a 

 triangular remnant and a minute dot. The right-hand spots of 

 these three are normal, resembling that of the male parent. The 

 left-hand spot of a single female (B) resembles that of the male 

 ])arent, the other four being normal or v\ith a slight trace of 

 asymmetry. 



Mr. Bacot bred from A and B, rearing in the 1902 family 4 

 males and 5 females. Of the males, two liave unich smaller spots 

 on the left, one of them being divided into two ; the other two 

 males show only slight asymmetry. Of the females, three show 

 the parental character but in an exaggerated form, the invasion 

 having been carried further, and starting in one of them from 

 the basal margin of the spot instead of its outer margin, as in the 

 others and the parents. A fourth female resembles that last 

 described, except that the invasion is into the right spot instead 

 of the left and has been carried further so that two small dots 

 representing the two outer angles of the spot are all that remain. 

 The fifth female is normal with little want of symmetry. 



No one who looks at the material can doubt that this small but 

 striking variation, affecting the shape of a single spot, is hereditary. 

 The series also affords evidence of another kind in favour of the 

 view suggested on p. 22, that Mendelian inheritance will be found 

 to hold in extremely small variations, as well as in large ones. 

 The hind wing in the female S. phe(jea bears two large patches, of 

 which the outer is generally accompanied by a small detached spot 

 lying on its upper (or costal) border. In the male both patches 

 are reduced to spots of which the inner one is especially small 

 and in most individuals represented only by its upper (or costal) 

 section, the lower section when present being minute and quite 

 detached. The evidence bearing on Mendelian inlieritance is 

 derived from the presence or absence of the small inner spot in 

 ihe male hind wing. 



Of the two 3899 males, one is normal while the other is as last 

 described, the lower section of the inner spot being much smaller 

 and barely visible on the right side. 



In the 1900 family six males are normal, in three or four more 



