188 EVOLUTION AND DISEASE. 
of an individual are in many instances transmitted to 
the offspring. Malformations, as such defects are called, — 
arising in this manner are usually classed as arrests of | 
development, and as it is clearly established that the — 
embryological history of a complex individual may be — 
regarded as an abbreviated history of its evolution, it 
necessarily follows that, should the development of a 
part be arrested at any particular stage, we should 
expect to find, in some less specialized mammal, this 
stage represented as a permanent condition. For ; 
instance, children are often born with club feet; the 
commonest congenital form is that which in the sole of | 
the foot looks inwards and upwards, and the heel is 
slightly raised (talipes equino-varus). In the child 
before it is born the feet are for several months in this 
position, and gradually pass into that assumed normally 
in the adult. Not infrequently the foot fails to assume 
a position at right angles to the leg, and malformation 
is the result. Now it is very instructive to remember 
that the orang’s foot is in the position typical of talipes 
equino-varus, and this is not limited merely to the 
position of the foot, but extends also to the disposition 
of the articular surfaces on the ankle-bone. 
It is far from my intention to enter in a detailed 
manner into all forms of malformation which may be 
transmitted ; that such characters are inherited is in- 
disputable, but it may be useful to describe an instance 
in which it has been possible to produce a permanent 
variety in which the existence of a malformation is the 
distinguishing feature. This is the more important 
because as a rule defects of this class appear sporadically 
