i i 



"^ E 



^r 



^ 



Figure 2. --Example of a "dry slice, 

 transverse," mounted on a 25 x 75 

 mm. slide; aiiterodorsal view; pelage 

 in early molt. 



Specimens 

 of Fibers 



Used for Estimating Abundance 



Using a special technique, skin samples of 

 measured area were collected from 21 seals 

 for the purpose of estimating abundance of 

 pelage fibers per unit area of body surface. 

 (1) On the back and belly of the freshly killed 



seal, the four corners of a 10-cm. square 

 were marked by injecting a few drops of black 

 waterproof ink through the pelage into the 

 dermis, (2) A square of skin-with-pelage in- 

 cluding the four black spots was removed by 

 knife and pinned flesh-side up on a slab of 

 wax, stretched slightly in order to restore the 

 dimensions as in life; then fixed in formalin. 

 (3) Later, a patch was sheared from the 

 pelage and circular plugs of skin were re- 

 moved, each 0.4 cm. in area. A trephine for 

 removing such plugs has been described by 

 Carter and Clarke (1957). (4) Each plug was 

 soaked with alcohol and dried between flat 

 surfaces. Its epidermal side was photographed. 

 From photoenlargements at 15 X, pilose- 

 baceous units per 0.4 cm. were counted. (5) 

 From other plugs in formalin, paraffin mounts 

 were prepared and individual fur fibers per 

 bundle were counted under a microscope. 



Age of Individual Specimens 



The study was designed to show the molt 

 characteristics of each year class to, and in- 

 cluding, the fifth, and of pooled classes above 

 the fifth. 



The ages of many individual seals collected 

 during the study are exactly known from 

 numbered tags which had been applied in the 

 first summer of life. The ages of others have 

 been estimated from annular layers on the 

 upper canine teeth. For certain individuals 

 where the tooth layers are obscure, or where 

 the field record shows simply "adult," or 

 "old," or "10+," an arbitrary age of 10 years 

 has been assigned to males and 12 years to 

 females. These individuals include 2 (or 1,4 

 percent) of 148 males in molt and 17 (or 8.9 

 percent) of 192 females in molt. 



Measurements 



In order to visualize and to describe the 

 procession of molt it was necessary at first to 

 take 11 measurements on each specimen. 

 Later, when diagnostic features of each stage 

 of molt were known, only six key measure- 

 ments were taken. The list follows: 



1, Color of underfur . — Munsell color of the 

 underfur on a dry mount lying ventroposterior 



