PEE-OCULAR AND POST-OCULAR TENTACLES OF NAUTILUS. 197 



The Pre-ocular and Post-ocular Tentacles and 

 Osphradia of Nautilus. 



By 

 Ai'tliiu* l¥illey, D.Sc. 



With Plate 10. 



The occurrence of a special tentacle in front of the eye and 

 another behind the eye in Nautilus is well known. These 

 tentacles resemble the large number of remaining tentacular 

 appendages in being ringed, and also in being retractile within 

 sheaths, but diflfer from them in almost every other respect. 

 In the first place, most of the tentacular appendages of 

 Nautilus have essentially an adhesive function, to which is 

 related a prehensile function. They are employed for seizing 

 hold of food and for attachment to surfaces. 



Attachment is effected by the definite suctorial ridges on 

 their lower and inner sides (fig. 3). When attached by its 

 tentacles. Nautilus holds on with considerable tenacity ; ^ and 

 sometimes in forcibly detaching it some of the tentacles 

 break off, and remain fixed to the surface of attachment. The 

 shape of a section of the tentacular processes of Nautilus is 

 that of a spherical triangle, the base of which corresponds to 

 the suctorial ridges, while the apex and sides are directed 



1 In the next number of this * Journal ' Dr. Willey's figure of a pearly 

 Nautilus crawling on a glass surface by means of its tentacles will be pub- 

 lished, as also some notes on the coelom and pericardium of Nautilus. His 

 discovery of the deposited^ eggs of the Nautilus has been published with 

 figures of the eggs in the ' Proc. Roy. Soc' 



