Speed of Racehorses 
of a snipe. In the case of racehorses, which 
have been selected so carefully through a long 
period of time, we seem to have reached the 
limit of speed which can be attained by the mul- 
tiplication of insignificant variations. We do not 
wish to dogmatise, but we believe that of late 
years there has not been any material increase 
in the speed of our racehorses. 
Mr S. Sidney says, on page 174 of Cassell’s 
Book of the Horse: “ As far as form went (pace 
Admiral Rous), the British racehorse had reached 
perfection in 1770, when ‘ Eclipse’ was six years 
old.” He quotes the measurements of the 
skeleton of “Eclipse” in the Museum of the 
Royal College of Surgeons as evidence of this. 
All the efforts of breeders, then, have failed 
appreciably to improve the form of the British 
racehorse in the course of over a century and 
a quarter. 
De Vries has made some important experi- 
ments with a view to determining whether or 
not there is a limit to the amount of change 
which can be induced by the selection of 
fluctuating or continuous variations as opposed 
to mutations. “I accidentally found,” he writes, 
on page 345 of Species and Varieties: ther 
Origin by Mutation, “two individuals -of the 
‘five-leaved’ race (of clover); by transplanting 
them into my garden I have isolated them and 
kept them free from cross-fertilisation with the 
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