Interesting read in last month’s magazine about a spontaneous mutation in Ruth’s shed. I have indeed had a similar thing occur in my strain of red brokens. One of the breeding trios that I had given to Lewis Russell had produced a mouse with a red patch among its cinnamon patch- es. Lewis had returned the young doe to me so I could try my hand in producing ‘proper’ tricolour mice. Unfortunately, despite four litters bred from this doe, mating it back to its son, as any breeder would have done, it never pro- duced one single tri in its life. Some mutations are somatic, i.e. they only happen at the cellular level in somatic tissues occurring after fertilisation. These muta- tions do not involve the germline and consequently do not pass on to offspring. So, a dead end, if a very attractive one!