THE WAX PLUG OF THE MYSTICETI 3°i 



laminations, it will be seen that the length of the core of the plug is not isometric with the body length. 

 This result can be explained by the great disparity between the rate of growth in length of the body 

 and that of the skull width in foetal and juvenile specimens, a feature of growth which is common to 

 all mammals. On the basis of this estimation, a male specimen from the southern hemisphere with the 

 same number of laminations as in Lillie's specimen (PI. XVIII) would be 18 years old and approxi- 

 mately 22 m. in length. 



The radiograph, PL XIV, fig. i , shows two wax plugs from the left and right side of a single specimen 

 of Balaenoptera physahis. The number of countable laminations in each specimen as ascertained from 

 the negative was eighteen and the general distribution of light and dark areas indicates that the rate of 

 formation of the plugs is bilaterally symmetrical. 



\i 20 



NUMBER OF LAMINATIONS 



30 



Text-fig. 2. Growth curve of the core of the wax plug in Balaenoptera physalus. 



It remains to comment upon the outer covering and the distal end of the plug which, as previously 

 stated, appears to be formed from the zona germinativa of the meatus. Since there is no apparent 

 periodic increase in the diameter of the lumen of the meatus, there is no necessity for periodic increased 

 development of its epithelium; indeed, the rate of development would need to be rather slow. The 

 restricted space would also necessitate the inhibition of ceruminous secretion and it will be recalled 

 that no evidence of ceruminous glands could be found. 



Whether lamina formation is a six-monthly or an annual event remains to be ascertained, but the 

 evidence obtained from this preliminary examination suggests that it is either one or the other and it 

 seems that further investigation is desirable. The extreme rarity of material is doubtless due to the 

 impracticability of dissecting out the external meatus of whales on the flensing platforms of factory 

 ships, but it should be possible to withdraw the wax plug from the meatus by way of the tympanic 

 cavity after the tympanic bulla has been levered out. 



