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(1) Because it was necessary to travel so far away from 
the species before a three-toed ungulate was found. 
(2) Because the toe did not appear in the position where 
it must have appeared, on this hypothesis, if received homo- 
logies of the toes were reliable. 
(3) Because precisely analogous cases had been found in 
the human subject. Six-fingered and six-toed men were not 
very uncommon ; and as no beast, bird, or reptile had more 
than five digits on each limb, and yet the extra fingers and 
toes were definitely human, this evidence was conclusive against 
the abnormality being due to atavism. 
The second cause might operate in two ways. The organic 
units might be stimulated to throw off more gemmules, or these 
gemmules might have enhanced affinities. In either case they 
might attach themselves to any nearly allied growing part 
between which and themselves there was an affinity resembling 
their natural one, and so by effecting a double attachment give 
rise to a double organ. Nor would the extension of the extra 
abnormal part to a fresh limb, as in the case of the young bull, 
be unaccountable. For the extra digit, being the direct de- 
scendant of a normal one whose organic units had been exces- 
sively proliferous, would resemble the parent part not only in 
- structure but in the vigour of its budding function. Thus we 
should have in the desired animal two energetic manufactures 
of gemmules instead of one, and in the third generation a still 
greater excess or avidity in the transmitted gemmules which 
would manifest itself in a fresh attachment. 
But if this were the true explanation of the peculiarity, 
it would follow that the extra digit, though it had the attach- 
ment of a finger, would be in reality, as im structure, a toe. 
It is difficult to draw a distinction between the toe and finger 
of an ox; but asa precisely analogous case had occurred in the 
human subject, they might safely reason from that. In the 
case referred to, the extra part had originated in the hands 
