The results of measuring the depth of under- 

 fur on 669 new samples are given in table 12. 

 The depth varies little with age, sex, or month. 

 Whether silver pups, middle-aged individuals, 

 or old ones, the depth is about 11.5 to 12.5 mm. 

 The mean for all males is 12.3 mm., for all 

 females 11.7; a difference of only 5 percent. 

 Maximum depth in males is 16 mm., in females 

 14 mm. 



From study of table 12 two conclusions may be 

 drawn. First, depth of underfur tends to decline 

 slightly with age. This probably results from the 

 spreading apart of the fur bundles as the body 

 surface increases. With more space around 

 them, the fibers assume a more wavy attitude 

 and, as a group, give the effect of a shallower 

 layer. Second, the tendency to effect a shallower 

 layer with age is, in the male, completely 

 masked by the rival tendency for fibers to grow 

 in length at age 5 and beyond, in the years of 

 s exual maturing. A spurt in growth of guard hair 

 length, especially in the mane, is easily seen at 

 this time. Probably the fur fibers also increase 

 in length. 



CHANGES IN COLOR OF THE PELAGE 

 The Change from Black to Silver in the Pup 



At birth the pup is wearing its fetal black 

 coat. Already, however, the adult-type coat is 

 beginning to form, deep in the dermis. In 

 September the pup coat changes from black to 

 silver. In 28 specimens taken between 1 

 September and 11 October (mean date 19 

 September), molt is in the following stages: 



Pups recorded in life as "black" 



Number in early molt 9 



Number in late molt 6 



Pups recorded in life as "silver" 



Number in late molt 7 



Number in ending molt..... 3 



Number resting in postmolt 3 



Thus it is evident that during late molt, when the 

 new guard hair tips have grown to or beyond the 

 underfur layer, the birthcoat hairs that give a 

 black appearance to the pelage are rapidly being 

 shed. The age of the individual when the change 

 takes place is not known, though it is certainly 

 near 3 months. Two pups of known age, 50 and 

 63 days respectively, would still be called 

 "black" (R.S. Peterson, in letter, 1961). 



Change in Color of the Underfur With Age, 

 Sex, and Season 



No differences in color of underfur attribut- 

 able to sex or season were detected in 48 dry 

 slices of pelage representing six age groups, 

 two sexes, and two seasons (spring and fall), 

 when all slices were displayed together on a 

 black table. With age there is a gradual shift 

 toward a darker and redder color. 



On the silver pup and yearling, the Munsell 

 colors are between "pale yellowish pink" and 

 "light grayish brown" (7,5 YR 8/2 and 6/2). The 

 fur is silvery to grayish with only a faint sug- 

 gestion of brown. Along the outer (distal) one- 

 third of its length the fur has a slightly more 

 brownish appearance; a result of pigment gran- 

 ules in thefiber cortex. Magnified, the granules 

 are seen as short rods 1 micron or less in 

 length, arranged parallel to the axis of the fiber. 



On the 2-year-old, the color tends to be dis- 

 tinctly darker and browner; between "light 

 grayish brown" and "light brown" (7.5 YR 6/2 

 and 6/4). An occasional light 2-year-old is like 

 a dark yearling. Between 2- and 3-year-olds, 

 the eye can detect a faint break. Between 3 's and 

 4's, and between 4's and 5's, the break is im- 

 perceptible. In the group older than 5 years, 

 however, most specimens are darker than the 

 subadults. Maximum color is seen in an old 

 male specimen; "moderate brown" (SYR 3/3); 

 a rich cocoa brown. 



Where the pelage fibers emerge from the skin 

 pore, and for a distance of about 1 mm. beyond, 

 they are brownish, as though stained. The color 

 is pale or absent in pelagic (first coat) year- 

 lings, and darker — up to chestnut — in full- 

 grown seals. Since the color does not extend into 

 the roots andsinceit appears concurrently with 

 the maturation of the sweat glands, it is probably 

 produced by the secretions of the sweat glands 

 at their point of exit. 



Appearance of White Guard Hairs in the 

 Male 



The presence of scattered large, white guard 

 hairs is a secondary sex character in the adult 

 male. White hairs may be seen in some 3- and 

 4-year-oIds, and in about one-half of the 5- 

 year-olds. One October 5-year-old shows 7 new 

 white guard hairs per linear cm. on a transverse 

 section. In old bulls, white hairs may compose 



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