EXTERNAL PARASITES OF WHALES 375 



figs. 2 and 4). Sometimes the crescent is short, as though only shght penetration had 

 occurred, at other times the scooping action seems almost to have been completed so 

 that the free flap of blubber and skin remains attached by a thread as it were to the 

 edge of the pit. A kind of scar tissue covers the blubber surfaces within the crescent 

 pit, and this peels at the edges during healing. 



In the healing stages the epidermal layer loses its sharp edges and grows gradually 

 inwards, while the blubber fibres grow up and draw together (Plate XXXVI, fig. 9). 

 Pigment is not present in the later stages so that when the wound is completely healed 

 the scar is white. In sections the scar tissue shows up as a mass of converging fibres 

 (Plate XXXVII, fig. 3). White crescent scars, formed probably by prompt healing 

 of a wound which never got beyond the initial stages, are found sometimes, but they 

 are not numerous. 



Careful examination of the whales at Saldanha Bay led to the discovery of occasional 

 crescentic grooves with a few minute slots in the course of the groove (Plate XXXVI, 

 fig. i). The slots led into a subcutaneous crescentic canal following the arc of the 

 surface depression. Microscopic examination of the contents showed nothing in the 

 canal but numerous bacteria. 



Specimens of all the stages observed have been collected from whales at Saldanha 

 Bay and South Georgia, and examined from the histological point of view. Sections 

 show a number of interesting points connected with the earlier stages and a possible 

 causative agent. As the primary cause of the pits remains in some doubt it is of course 

 not certain that the stage of the curved groove with its minute punctures is connected 

 with the pits. It seems logical, however, to connect this stage with the crescent-shaped 

 incisions. If one imagines a continuation of the process forming the crescent fiap and 

 the final throwing off of the latter, an open pit will be formed. Thus the stages fall into 

 a natural order, beginning with the arc-shaped groove and the epidermal canal followed 

 by the crescent pit. Occasionally this heals, to form the crescentic scar, but more 

 frequently the whole centre is thrown off leaving scar tissue over the surface of the 

 exposed blubber. This is sloughed off as the flabby disc referred to above, and leaves 

 the clean open pit (Fig. iii). 



It is quite probable that the initial stages are more frequent in regions further north 

 than Saldanha Bay. This is suggested by the difficulty of obtaining evidence as to the 

 primary cause of the pits and by the fact that whales in the colder waters of the south 

 show only scars and a few late healing stages. It is reported by Olsen (1913) that 

 wounds "filled with mortifying fat " were very numerous in the few old and apparently 

 diseased specimens (of Bryde's whale, B. brydei) taken at Port Alexander, which is 

 over 1000 miles north of Saldanha Bay. Similarly, the blubber of whales off the coast 

 of Ecuador is, according to Risting, often more or less covered with deep holes filled 

 with matter. 



Sections of the arc-shaped groove show a deep cleft in the pigmented epidermal 

 layer. In the blubber beneath is a wedge-shaped mass of tissue with deeply staining 

 nuclei (Fig. 112). In this area the blubber has been completely replaced by this 



