198 ARTHUR WILLEY. 



outwards^ and are distiuguislied by a deep brown pigment. 

 The suctorial ridges have a pale neutral tint. We may, there- 

 fore, speak of those tentacles which are used for prehension 

 and attachment as the adhesive tentacles. Their function 

 speaks for the pedal nature of the tentacular processes of 

 Nautilus, as does also their innervation; and further, their 

 function allows them to be compared with the arms of the 

 Dibranchiata. If the comparison is carried into detail the 

 suctorial ridges of the former would correspond with the 

 definite suckers of the latter. 



That prehension as well as adhesion is a function of the 

 Molluscan foot is well illustrated by the method of capture of 

 a species of Oliva at Lifu. This species can be obtained in 

 large numbers by employing a line baited with the animal of 

 a land-shell (Placostylus). The Oliva wraps its foot round the 

 bait, and so can be lifted out of the water and landed. 



Recently arguments have been brought forward by Kerr^ 

 against the supposed pedal nature of the Cephalopod arms in 

 general and the tentacular processes of Nautilus in particular. 

 If embryological data are not to be trusted on account of the 

 large quantity of food-yolk in Cephalopod ova, we are obliged 

 to consider, among other things, function and innervation. 

 With regard to the latter, Kerr throws doubt on the generally- 

 accepted identification of the sub-oesophageal ganglionic 

 masses of Cephalopods. It is well, however, to remember 

 that in Dentalium the ganglionic centres have the same 

 topographical relations as in Nautilus, the undoubted pedal 

 ganglion being placed far in front of the pleural and visceral 

 ganglia. 



Returning to the tentacular appendages of Nautilus, it will 

 not be surprising to learn that the adhesive tentacles are not 

 ciliated ; but it is necessary to mention this negative fact, 

 because the pre-ocular and post-ocular tentacles are ciliated. 

 On the side corresponding to the suctorial ridges of the ad- 

 hesive tentacles the annulations of the pre- and post-ocular 



' J. Graham Kerr, "On some Points ia the Anatomy of Nautilus pom« 

 pilius," 'Proc. Zool. Soc.,' 1895. 



