Nov.. 1889. 
THEORIES OF HEREDITY. 
255 
with a very high degree of probability, to have followed the 
lines indicated in Diagram III. 
The amount of resemblance has been shown by Gal ton,''*' 
who traced the after life of about eighty “ identical” twins as 
far and as completely as possible, obtaining instructive details 
in thirty-five cases. Of the latter there were no less than 
seven cases “ in which both twins suffered from some special 
ailment or had some exceptional peculiarity in nine cases it 
appeared “ that both twins are apt to sicken at the same time 
in eleven cases there was evidence for a remarkable association 
of ideas ; in sixteen cases the tastes and dispositions were 
described as closely similar. These points of identity are 
given in addition to the more superficial indications presented 
by the failure of strangers or even parents to distinguish 
between the twins. 
When the lives of twins were followed in after vears “ in 
«/ 
some cases the resemblance of body and mind continued up 
to old age, notwithstanding very different conditions of life.” 
In other cases “ the parents ascribed such dissimilarity as 
there was wholly, or almost wholly, to some form of illness.” 
The conclusions of the author are as follows :—“ Twins 
who closely resembled each other in childhood and early youth, 
and were reared under not very dissimilar conditions, either 
grow unlike through the development of natural characteristics 
which had lain dormant at first, or else they continue their 
lives, keeping time like two watches, hardly to be thrown out 
of accord except by some physical jar. Nature is far stronger 
than nurture within the limited range that I have been careful 
to assign to the latter.” And again -‘where the maladies of 
twins are continually alike, the clocks of their two lives move 
regularly on, and at the same rate, governed by their internal 
mechanism. Necessitarians may derive new arguments from 
the life histories of twins.” 
Mr. Gallon also met with twenty cases of twins (also of 
the same sex) in which the differences were greater than 
those which usually distinguish children of the same family. 
In such twins the conditions of training, &c., had been as 
similar as possible, so that the evidence of the power of nature 
over nurture is strongly confirmed. Mr. Galton writes, “ I 
have not a single case in which my correspondents speak of 
originally dissimilar characters having become assimilated 
through identity of nurture. The impression that all this 
evidence leaves on the mind is one of wonder whether nurture 
can do anything at all beyond giving instruction and pro¬ 
fessional training.” 
* Journal of tbe Anthropological Institute, 1875, p. 891 and p. 325. 
