CONCLUSIONS. 561 
to another manner of living, compelled thereto by certain circum- 
stances. They viz. took to eating fresh water fish. Gradually this 
crew to be a habit; they learned to swim, which happened by 
vertical undulations, they paddled with the feet, and used the 
tail as a rudder. This group may be called long-tailed ancestors of 
polecats and minks, for our common polecat (Putorius putorius L.) 
and the Russian minks (Puéforius lutreolus L.) are still livmg des- 
cendants of them, though the tail has become short, because they 
have accustomed themselves to live in holes. The long tail has 
shown itself to be an inconvenient organ for such a manner of 
living, and therefore has gradually become shorter, not so short, 
however, as in weasels and stoats. Zoologists place the polecats and 
minks in the same genus as the weasels and stoats. The minks 
live especially in the neighbourhood of rivers and brooks, often go 
into the water and swim exceedingly well. Besides on poultry and 
rats, they feed on frogs, crabs, cray-fish, and all kinds of fish. 
Some of these /ong-tailed ancestors of polecats and minks got so 
used to the water, that it finally became their proper element, 
and they came ashore only to rest from swimming, to bask them- 
selves in the sun, or to find another brook or river. They began 
to feed on fish, crayfish, and frogs, and only when driven by 
hunger they fed on rats and poultry. It is evident that those 
individuals which by nature were best adapted to their new ele- 
ment, must gradually have survived their less privileged brethren , 
and so we may admit that a form gradually arose, wich swam very 
easily with vertical undulations, using the tail as a rudder and as 
propelling organ. Also of great advantage must have been more 
sharply pointed teeth, and more jagged molars, smaller ears, a 
more woolly skin, and toes on the hind lmbs, which were capable 
of expansion and more or less provided with a web. This group 
may be called Jong-tailed ancestors of otters, for all the known 
species of otters (Lu/ra) are still living descendants of them, though 
the tail has become shorter, shorter than one third of the total 
length of the animal, because they too like to live in holes. The 
face greatly resembles that of the polecat and mink, but the upper 
lips are thicker and the whiskers are longer and stronger. ‘The 
change was not only great enough for zoologists to create for this 
group a new genus: Lutra Srorr, but even to establish for it a 
new subfamily Lutrina Gray. 
These /ong-tailed ancestors of otters were again survived by their 
congeners which were still better adapted to the new medium, so 
36 
