of collection, p. 4). The sample includes 9 The rate of change is -33.2 per year. The 

 males taken in July to November 1961 and 12 linear equation, Y = 1,168-33.2X represents the 

 females taken in July to October 1961 (table relationship of the number of fur bundles per 

 16). cm. 2 with age. It is evident that, as long as the 



seal continues to grow in size and surface 

 Effect of Age area, the average distance between pilose- 



baceous units increases. 

 The counts of fur bundles per cm ^ on the 

 back are, for the From the foregoing table, the mean number 



of fur bundles per cm. 2 for two 12-year 



3-year male (N = 3) 1,296 females is 929. Multiplying by 45, the estimated 



4-year male (N = 6) 1,096 number of fur fibers per bundle (table 11), the 



5-year female 1,108 product is 41,805 fur fibers per cm. 2^ or 



6-year female 1,073 269,642 per inch 2, The latter figure is believed 



7-year female 981 to be a more precise estimate than an earlier 



8-year female 1,098 one, 370,000 per inch 2, given by Scheffer 



9-year female 965 (1962, p. 7). 



12-year female 930 



"Adult" female, estimated age 12 Effect of Sex. 



years 928 



15-year female 790 With respect to pelage fibers and thickness 



of skin, the subadult male and the adult female 



The number of fur bundles per cm. 2 de- of comparable size are similar (table 16). The 



creases with increasing age of seal (P< .01). male fibers tend to be slightly longer and more 



Table 16. — Comparison of pelage, male and female of the northern fur seal, 



back and belly""" 



Mean values 



Male 



Female 



Age , years 



Length, cm 



Weight, kg 



Slant depth of dermis on back, mm 



Slant depth of dermis on belly, mm 



Depth of guard hair on back mm 



Depth of guard hair on belly, mm 



Depth of underfiir on back, mm 



Depth of \anderfur on belly, mm 



Number of \mderfur bundles per cm. ^ on 



back 



Number of underfuT bundles per cm.^ on 



belly 



Number of underfur fibers per bundle on back 

 Number of londerfur fibers per bundle on 



belly 



1162.7 



1188.2 

 31.6(2) 



1012.0 



1066.0 

 44.9(3) 



41.2(2) 



""■ On 9 male and 12 female seals from which equal-area squares of skin were 

 removed. Where a mean value is based on fewer than 9 males or 12 females, N 



is shown in parentheses . 



31 



