294 



THE CEPHALOPODA 



It follows that in all living Cephalopods except Nautilus the 

 shell is localised on the anterior or physiologically dorsal side of 

 the body, and is enclosed by the mantle, which therefore appears 

 to be a naked, bell -shaped sac (Figs. 252, 254, 287, etc.). The 

 whole circumference of the mantle border is free in the Decapoda 

 (Fig. 259), with the exception of Sepiola, in which it is fused to the 

 head anteriorly in the middle line. Similarly, in the Octopoda, the 

 border of the mantle is fused to the head anteriorly and laterally, 

 whereby the pallial aperture is much reduced, especially in Cirrho- 



teuthis (Fig. 260) and Opisthoteu- 

 this (Fig. 300). 



In the Decapoda a more secure 

 union between the mantle and 

 the funnel, during the expulsion 

 of the water used in respiration 



m 



FIG. 259. 



Ctetiopteryx cyprinoules, ventral aspect. 

 a, arms ; e, eye ; fi, fins ; /it, funnel with 

 valve ; ol, olfactory organ or rhinophore ; 

 so, socket of the funnel ; te, tentacular 

 arms. (After Joubin.) 



FIG. 200. 



Cirrhoteuthis meangensis, Hoyle (young speci- 

 men), ventral aspect, ji, fin ; fit, funnel ; in, 

 mouth. (After Hoyle.) 



through the latter structure, is ensured by the following mechanism : 

 the free borders of the mantle bear on each side a cartilaginous pro- 

 jection (Fig. 272, c) which fits into a corresponding depression in 

 the funnel (Figs. 272, c ; 259, so), the whole constituting the so- 

 called " resisting apparatus " of foreign authors. In certain Oigopsida 

 of the family Cranchiidae (Cranchia, Leachia) and in the Octopoda 

 this apparatus is but feebly developed, and in Cirrhoteuthis, where 

 it would be useless, it has disappeared. Otherwise the funnel is 

 quite independent of the mantle : it is only in Amphiirdns among 

 the Cirrhoteuthidae that the mantle -border is united to the 

 funnel by a ventral suture, leaving an opening into the pallial 

 cavity on either side. Similarly, in Grinialditeuthis and Symplecto- 



