106 Dr Jobn Struthers on Variation in the Number ~ 
atavism, it is lable to be lost at every new union, and, we 
would suppose, liable to be worn out at last. The case of 
the L family (case 15) illustrates various phenomena 
of variation and transmission. (1.) In the line of descent 
through Andrew L , we see three successive generations 
without the variety, and it is apparently extinguished. 
(2.) In the line through James L , he and his children 
were normal, but it re-appears in his grandchildren, having 
passed over two generations. In case 19, it had passed over 
three, and in case 16, over at least two, generations. In 
case 18 (a) although the grandmother’s brother had it, 
the great-grandparents had not, so that it had passed over 
three generations in the direct line and reappeared in the 
fourth. 
(3.) We see uninterrupted transmission in the line of 
descent through John L , from Ksther in the first (if 
she was the first), to Jane in the fourth generation. The 
six-fingered tendency had here maintained itself against 
three successive unions with five-fingered persons. In the 
first offspring it succeeded, as far as we know, in only one 
out of 18. In the offspring of this one (Charles L ) 
it succeeded in 3 out of 12. In two of these three it did 
not appear in the next generation ; in the third of them it 
succeeded in one out of two children, thus being directly 
transmitted to the fourth generation. 
It is interesting to notice, too, how the variety so far 
from being weakened had gathered force in each new 
generation, even although it had not the advantage of the 
greater development attending utility, to enable it to in- 
crease its hold on the organism. In the first known 
ancestor (case 15) it occurred on one hand; in the second 
generation on both hands; in the third on both hands of — 
two brothers, and on both hands and one foot of a third 
brother ; and in the fourth generation on all the four limbs 
—thus, so far from becoming weaker, making its way to an 
additional limb in each successive generation. 
Besides thus extending itself symmetrically and serially, — 
it may extend in depth, beginning as one phalanx and — 
extending at length to the metacarpal or metatarsal region. 
In some of the cases of original variation, there was only — 
