176 DISCOVERY REPORTS 



Ridewood concludes that the bonnet of the Southern Right whale would appear to 

 be a circumscribed area of skin, where, for some reason not apparent, the cornified 

 layers fail to rub off at their normal rate, but remain and accumulate to produce a hard 

 mass, projecting above the general surface of the epidermis as a kind of corn. I have 

 been unable, after examining microscopic sections prepared from well-preserved 

 material, to find any essential difference between the structure of one of the smaller 

 callosities and that of normal skin, except that the outer cornified layers are thicker. 



On two occasions different members of the Discovery Staff, when examining Right 

 whales, noted that the callosities on the mandible "may have marked the position of 

 hairs" (whale No. 503, 26. viii. 26), and "their appearance suggested that they may 

 have been occupying the position of hair follicles" (whale No. 3560, 14. i. 31). The 

 callosities occupy just those positions where hair groups would be found in other 

 whales, and the opinions expressed above, being those of men who have examined 

 many hundreds of whales, strongly support the suggestion that the bonnet and other 

 callosities represent hair groups of other whales. The callosity over the eye would thus 

 represent the eyebrow, a feature unknown in other species. 



The occurrence of fully developed callosities in whale No. 1020, a sucking calf, shows 

 that they are congenital and not developed after adult life is reached, as do those recorded 

 in a foetus by Lonneberg (1906). In view of the fact that the callosities are the centres 

 of the heavy infection by cyamids that is always found on this species of whale (see 

 below, external parasites), one wonders whether there may not be some truth in the 

 suggestion that they form a basis for some sort of commensal relationship between 

 parasite and host. The advantage to the parasite of these thickened areas both for pro- 

 tection and food is evident from their concentration in them. The advantage to the host 

 is more problematical, but it seems possible that the localization of the parasites on 

 special areas of thickened epidermis may save the host the irritation presumably caused 

 by such large numbers, were they scattered at random on the thinner parts of the skin. 



Allen (1908) speaks of "the well-known function of this structure [the bonnet], as 

 the nidus of parasitic Crustacea, by which its growth is promoted, if not originally 

 caused". This view cannot be correct, for it has been shown above that the bonnet and 

 other callosities were present in a young calf; further, the situation and relative size of 

 the bonnet and other callosities is constant, and parasitic Crustacea, though concentrated 

 in them, are not confined to the callosities. Again, why do not other species, especially 

 the Humpback, which are also infested with cyamids, have callosities? 



Andrews (1909) gives excellent photographs of the callosities and their associated 

 swarms of parasites in the Northern Right whale. They are exactly similar in every 

 respect to those of the present series of whales. Lonneberg (1906) also illustrates 

 callosities of the Southern Right whale from South Georgia. 



PALATE AND TONGUE 



No. 10 1 9. The whole palate, from the oesophagus almost to the tip of the snout, is a 

 narrow pinkish strip, of a uniform width of about 3 in., and with a groove at the anterior 



