AQUATIC MAMMALS 



proportions. It is situated fairly between the spermaceti organ and the 

 adipose cushion below. It has a large diverticulum between the organ 

 and the skull and another anterior of the organ, and joins the left nos- 

 tril just within its orifice. The mucosa of the left nostril is plicated 

 but that of the right is smooth in Physeter. In Kogia, whose spermaceti 

 organ and nasal passages are relatively very much shorter indeed, the 

 mucosa of the right passage is thrown into complex folds, evidently in 

 compensation for its shortness. These folds, according to Kernan and 

 Schulte, are highly vascular. 



It seems almost certain that originally the narial conditions of the 

 sperm whales were very similar to those found in other odontocetes. 

 At least we are justified in assuming so, for the conformation of the 

 skull indicates that there was retrogression of the external nares to the 

 top of the head in the sperms as in other toothed whales. What I be- 

 lieve to have since taken place in the case of the latter is a secondary 

 displacement forward of the blowhole proper and its controlling mus- 

 culature by crowding of the spermaceti organ, although H. C. Raven 

 is of the opinion that the organ began to develop in front of the nos- 

 trils and intruded between them as it increased in size. Ordinarily ex- 

 piration and inspiration in this group must be accomplished solely by 

 means of the left nostril. At least it seems certain that because of 

 the disparity in size between the right and left narial apertures of the 

 skull an insignificant amount of air could pass through the former during 

 the short time occupied by the act of breathing. But the enormous dila- 

 tion possible in the case of the right passage can hardly be fortuitous and 

 must have some function. If it be dilated with air, as seems certain, then 

 this should occur chiefly between breaths. It might hold an accessory 

 air supply, but hardly enough to account for the long submergence of 

 these whales, which are purported to remain below in excess of an hour. 

 It is not impossible that the right nostril may be emptied of air to facili- 

 tate deep diving, and filled from the lungs so as the more easily to bring 

 the animal straight up from the depths, as suggested by H. C. Raven 

 (MS) . And one must not overlook the possibility that when beneath 

 the surface for a considerable period a part of the air in the lungs might 

 be forced into the right passage and again withdrawn for some particular 

 physiological purpose which might or might not have something to do 

 with the spermaceti organ. 



No discussion of the position of the external nares in aquatic mammals 

 has yet been made in the present contribution. The position will cor- 

 respond to the sort of stimulus experienced, the length of time that it has 



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