They were probably the colorless tips  hairs which had not yet grown out
to
of young guard hairs. Black pigment the dark portion. This idea was
spots were numerous in the belly re- strengthened by the fact that white-
gion, thinning out and disappearing  tipped hairs with short dark bases
anterior to the posterior portions of  were emerging from  dark pigment
the forelegs, and posterior to the anter- spots. Flesh surfaces, with few
chang-
ior portion of the hind legs. These ap-  es, were pigmented similarly to
the
peared to be guard hair pigments from  5-day-old kit.
newly forming guard hair into which  10 Days. Many dark guard hairs
they were observed to merge. They  were emerging on the belly at 10 days
were not numerous enough to give   of age. It was not possible to determine
color to the belly region; most could  if fur hair was present on the belly
be observed only under magnification. region since none could be plucked.
This intense growth of dorsal guard  A darkening of the ventral flesh sur-
hairs was reflected on the dorsal flesh  faces made it probable that fur
hair
surface of the skin by a very dark pig-  was beginning to erupt. The dorsal
mentation. Ventrally, the flesh side  area now had a fair number of fur
was light colored, corresponding to the  hairs among the guard hair.
virtual lack of hair growth.         11 Days. The ventral surfaces were
  From these findings it would appear  well covered with both dark guard
that on both the ventral and dorsal hair and fur hair, except on the throat
surfaces guard hairs are the first type  region and between the bind legs.
of hair to develop.                    Ventral flesh surfaces were dark ex-
  5 Days. Pigment spots on the belly  cept in the throat region and on the
appeared to elongate and the dark  inside of the legs-the same areas
portion of the new guard hair shafts 'showing the least amount 'of hair
were beginning to emerge. Because  covering.
the guard hairs were still only a short  17 Days. The throat region was still
distance out of the skin they lay at a  only thinly covered at 17 days and
very acute angle-almost parallel to  the flesh surface in this region was
the skin. Fur hair was not yet visible. still light.
Only a slight darkening of the flesh  22 Days. The kit had a good coat of
side had occurred ventrally, and dor- fur all over and fur growth was begin-
sally the flesh side remained heavily  ning to cease in the mid-dorsal areas.
pigmented.                             Pigmentation was also disappearing
in
  7 Days. There was still no apparent this region.
sign of fur hair. If it was present it  26 Days. The flesh surfaces were
must have been extremely short. At practically white in the mid-dorsal
any rate, it was not possible to pluck  area at 26 days of age as hair produc-
anything but guard hair for micro-  tion in this area ceased, but intense
scopic examination. There wvas an in-  hair growth and accompanying pig-
creased number of white hairs on the  mentation were evidenced in the belly
belly, and these in many cases were  area.
colorless guard hairs. They were prob-  30 Days. By this time the young
ably the colorless tips of dark guard  muskrat was fully furred with its
first

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