Cris,
Finally got my reference back.  Here's what I found.  It is the "1990 Public
Information Manual" , published by the California Domestic Ferret
Association; written by William, W.B and Shimbo, F.  Published by Ferret
Unity and Registration Organization Inc. 1990.
 
". . . many now feel that the ferret is decended from some now extinct
species which was bred in captivity and is most probably North African or
Spanish in origin"  Herter, K. "The Mustelids" Grimzek's Animal life
Encyclopedia, Simon & Shuster, 1976, pgs 37-68
 
It goes on to list the following differences between ferrets and polecats:
 
FERRETS
Colors range from albino to bicolored and tri-colored.  Eyes may be broun,
hazel, dark or light blue, grey, plum or red.
 
Skull pointed with eyes facing sideways; little binocular vision.  Typically
acrohhobic.
 
No cones present in retina, rendering ferrets colorblind.
 
All colors of ferrets have their visual systems wired as if they were
cross-eyed.
 
Unable to locate short bursts of sound in space.
 
Average litter size 10 +/- 2 . . . may produce two to three litters per year.
 
Fathers will assist raising the young if given opportunity.
 
Unable to tolerate extremes of heat or cold.
 
Thick skinned.  Fur falls out of pelt withing a year.
 
37 to 43 chromosomes, typical with number differences occuring between body
parts and also between sexes..
 
No typical greeting gesture.
 
POLECAT
Skull blunted with eyes facing forward; good binocular vision.
No acrophobia.
 
Coats only dark sable; eyes uniformaly brown.
 
Cones present in retina; can distinguish between red and blue.
 
Can locate sounds well in space quite well.
 
Average litter size is 6.  Only one litter produced per year.
 
Fur stays on pelts and is finer in texture.
 
Both sexes have 40 chromosomes.
 
Greet conspecifics with a "token attack"
 
Sources as given in the 1990 Info Manual: Harding, (1943), Fox (1987), Poole
(1966,1967, 1972), Basurur (1966), Apfelback and Webster (1977)
 
Sorry I took so long.
[Posted in FML issue 0983]