194 CEYLON PEARL OYSTER REPORT. 



may, therefore, be adopted as a working hypothesis. Dr. AsHWORTH has called my 

 attention to their similarity to the lateral organs of Annelids, described by ElSIG ('87) 

 and himself (:01). 



With respect to the function of the papilla as a whole, the most plausible 

 explanation appeared to me that they are protective. In the spirit specimens they 

 are not altogether unlike the tentacle-bearing heads of polyps, such as Hydractinia, 

 and I thought they might furnish the Octopus with a disguise to assist it in 

 concealing itself. Professor Herdman, however, tells me that this theory does not 

 agree with his observations on the living animal, which he kept for some time in a 

 small tank. Under these conditions " the papillae do not look at all like polyps ; they 

 are contractile and are kept frequently moving uncoiling to a considerable length 

 and then curling up again suddenly." 



Polypus aculeatus (d'Orbigny) ; Goodrich ('96) Plate II., figs. 10 and 13. 



Localities : Pearl Banks, Gulf of Manaar, Cheval district. Ten specimens 

 [197, male (?) ; 218-221, female; 266, male; 276, female; 630-632, sex (?)]. 



Station LVL, half-a-mile east of Dutch Modragam. One specimen, sex (?) [200]. 

 . The coloration of these young specimens so closely resembles that of d'Orbwny's 

 species (Octopus aculeatus) that I feel but little hesitation in referring them to it. 

 This identification is confirmed in most instances by the presence of small tubercles 

 arising from the centre of the pale circular patches on the upper surface. The general 

 appearance of these examples is shown in Plate II., fig. 13. 



Specimen 197 was very small, only 5 millims. in length from the end of the mantle 

 to the eye ; the patches were indistinct and no tubercles were visible, so that the 

 determination is less certain than in the other cases. 



Specimen 266 was the largest, and measured 15 millims. from the hinder end of 

 the body to the eye. The hectocotylised arm (Plate II., fig. 10) had apparently been 

 mutilated and subsequently repaired. It is normal up to within 2 centims. of the 

 extremity ; there it becomes swollen up (a) and the suckers suddenly cease ; the 

 groove on the ventral aspect (/;) runs out on the surface where the suckers should 

 be and stops abruptly, about 5 millims. beyond the gap in the series of suckers. 

 From this point there grows out a new tip, quite normal in appearance and about 

 10 millims. long (c). A new groove ((/) has been formed, starting from a point a 

 little beyond the place where the original groove ceases and quite disconnected from 

 it, and the usual spud-shaped extremity has been formed at the apex of the arm 

 (e). This reproduction is of special interest by reason of its rarity. Steenstrup 

 ('56, p. 107, footnote) was of opinion that the hectocotylised arm was never replaced, 

 and that consequently the animals exercised special care in order to prevent injury to 

 it. The examination of this specimen further raises the interesting question : If the 

 function of the groove be to transmit the spermatophores, could this action be carried 

 out in the event of the groove being interrupted ? 



