WHALES AND THEIR CLASSIFICATION 13 



to meet the posterior nares, forming a continuous 

 canal down which air passes from nostrils to lungs. 

 Cetaceans must rise to the surface to breathe, but 

 the expiration occurs at longer intervals than in 

 land mammals. 



The water vapour expelled along with the air 

 from the lungs condenses into the cloud visible 

 when the whale " spouts " or " blows," which is 

 nothing more than the ordinary act of respiration. 



The testes are abdominal and there are no 

 seminal vesicles. The mammce are two in number, 

 the nipples being placed in depressions on each side 

 of the vulva. The principal ducts of the mammary 

 gland are, during the period of lactation, much 

 dilated, forming large reservoirs in which the milk 

 collects. From these reservoirs it is ejected by the 

 action of a compressor muscle into the mouth of the 

 young, and by this means the process of suckling in 

 and under water is facilitated. 



Usually one young is born at a time, rarely two 

 and never more than two. 



The sexes are easily distinguished. Details of 

 the reproductive organs and " pairing " have been 

 published for porpoises by Meek. 1 Off the east 

 coast of England porpoises pair in July and 

 August, and they are frequently taken at this time 

 by the salmon net fishermen of Cullercoats. The 

 summer inshore migration of these creatures is 

 doubtless for the birth of the young and pairing. 



1 " The Reproductive Org-ans of Cetacea," by A. Meek, 

 Journal of Anatomy, Vol. lii., p. 186. 



