HORNLESS CATTLE AND OTTER-SHEEP. 215 
a stable door the tail of a bull was wrenched off, and the 
calves begotten by this bull were all born without a tail. 
This is certainly an exception; but it is very important to 
note the fact, that under certain unknown conditions such 
violent changes are transmitted in the same manner as 
many diseases. 
In very many cases the change which is transmitted and 
preserved by adapted transmission is constitutional or in- 
born, as in the case of albinism mentioned before. The 
change then depends upon that form of adaptation which 
we call the indirect or potential. A very striking instance 
is furnished by the hornless cattle of Paraguay, in South 
America. A special race of oxen is there bred which is 
entirely without horns. It is descended from a single bull, 
which was born in 1770 of an ordinary pair of parents, and 
the absence of horns was the result of some unknown cause. 
All the descendants of this bull produced with a horned cow 
were entirely without horns. This quality was found 
advantageous, and by propagating the hornless cattle among 
one another, a hornless race was obtained, which at present 
has almost entirely supplanted the horned cattle in Paraguay. 
The case of the otter-sheep of North America forms a similar 
example. In the year 1791 a farmer, by name Seth Wright, 
lived in Massachusetts, in North America; in his normally 
formed flock of sheep a lamb was suddenly born with a sur- 
prisingly long body and very short and crooked legs. It 
was therefore unable to take any great leaps, and especially 
unable to leap across a hedge into a neighbour’s garden 
—a quality which seemed advantageous to the owner, as the 
territories were divided by hedges. It therefore occurred to 
him to transmit this quality to other sheep, and by crossing 
