When autumn came its now longer winter coat lost the spots and became so pale as to be difficult to see towards dusk." This indicates a chinchilla mutation instead of albinism. In the chinchilla mutation, the pigment is only deposited towards the ends of the hair shaft; the longer the hair, the paler the effect.
This description implies that the chinchilla's coat coloration changes with the seasons. The specific characteristics of its winter coat, such as the loss of spots and paleness, suggest a genetic variation rather than albinism. This condition affects the distribution of pigment in the hair shafts.