354 REPORTS OF BERING SEA COMMISSION. 



Expiatiatiou o f ^^ jg-gj.gj^t pai'ts, bv meaiis of which it is attempted 



cliugramB. r ^ j l 



to represent the numbers of the different classes 

 of seals. We can fix the ages for 'killable 

 seals' with certainty, and all included under that 

 head are represented in the diagram by that 

 portion colored red. Male seals not killable and 

 not old enough to take a place on the breeding 

 rookeries are shown in green, while those of the 

 breeding age are shown in yellow. The lines of 

 demarcation up to this point are quite accurately 

 known and the diagram may be regarded as 

 correct, but we do not know certainl}^ at what 

 age the male becomes impotent and is diiven off 

 the rookery. The best estimate based on 

 analogies of other animals, places this period at 

 about the age of seventeen years, and the dia- 

 gram so represents it. 



In the classification of female seals there is 

 some difficulty, for while we are tolerably certain 

 that the young female goes on the breeding 

 rookeries at least at the age of three years, we 

 know little about the age at which she becomes 

 barren. The assumption that this period is 

 reached, on the average, at the age of eighteen 

 years, is, perhaps, not very far from the truth. 

 The younger females under the breeding age 

 are presented in green, the breeding females in 

 yellow, and the barren in brown. 



