EXTERNAL PARASITES OF WHALES 



377 



<^ 





rv.-; 



and might result from a wound or abrasion of some kind. In sections of the flabby disc 



(Fig. 114) he found a number of ciHated protozoa 



(Fig. 115) embedded in the tissue by which the base 



of the disc was attached to the bottom of the pit. He 



considered that these might quite hkely be the cause 



of wounds if the epidermis had been damaged sHghtly 



to allow their entry. 



On the under surface of the free edge of the flabby 

 disc there are matted ribbons of what look like rod- 

 shaped bacteria (Fig. 116). From their position one 

 would suppose that these are a secondary infection. 

 The flabby disc itself consists of an outer zone of 

 disintegrated cells. Farther in are dead blubber 

 cells. Beneath these is a zone of inflammatory tissue 

 and then come the fibres already mentioned in which 

 the protozoa were found. 



In seeking the cause of these pits we must consider 

 a number of possible agents. The balance of proba- 

 bility indicates that they are primarily the work of 

 micro-organisms, but this cannot be regarded as 

 proved. On the other hand, it does not seem possible 

 to explain the various stages by any of the theories 

 previously advanced. Coronula (Goodall, 1913), 

 Pennella (Olsen, 1913), and sucking fishes (Olsen, 

 191 3) have all been blamed, and biting fishes have 

 been suggested. Lillie (19 15) supposed that open 

 wounds of evidently the same nature in Humpbacks 

 at New Zealand had been caused by damage from 



sharp rocks. Fig. 114. Section of the "flabby disc." 



Taking these in turn it can be shown first that «, dead cells of surface disc; 6, heavily 

 ^ / 1 11 1 -1 1 rT-i • V nucleated tissue; c, protozoa; ^, base 



Coronula can hardly be responsible. This parasite of attachment to centre of pit. 



leaves a surface impression, but even when somewhat 





■si^ 



Fig. 115. Ciliated protozoa in scar tissue. 



embedded in the skin it does not penetrate below the pigmented epidermis (Plate 

 XXXVII, fig. i). When the furrows and ridges of the impression have flattened out 



16 



