710 ZOOLOGY SECT. 



The trunk is covered over by the thick integument of the mantle, 

 which terminates toward the oral end in a ridge round the neck. 

 Anteriorly this ridge projects as a prominent rounded lobe under 

 cover of which the head can be partially retracted. Posteriorly it 

 forms the posterior lip of the opening of a large cavity bounded by 

 the mantle the mantle-cavity which extends along the entire 

 posterior face of the body almost to the apex. The wide cleft 

 between the oral edge of the mantle and the posterior surface of 

 the body is not the only aperture leading into the mantle-cavity. 

 On the oral side of this cleft is a large tube the funnel (Fig. 621, 

 inf.) opening on the exterior behind the neck, and internally 

 communicating by a wide aperture with the mantle-cavity. The 

 cleft is capable of being almost completely closed by che 

 apposition of a pair of oval projections (mant. cart.) of the 

 inner surface of the posterior mantle wall near its oral border, 

 and a pair of concave depressions (inf. cart.) on the opposite 



s**f/* TTLU 9 



Fie. 616. Sucker of Sepia. A, oblique view of a sucker magnified; car. cavity; circ. mug. 

 circular muscle ; dent, denticulated border ; pi. muscular plug ; . stalk ; B, vertical section. 

 (After Vogt and Jung.) 



(posterior) face of the funnel. The funnel is thus, under ordi- 

 nary circumstances, the main outlet of the mantle-cavity. 

 As such it not only carries to the exterior the effete water 

 of respiration, the faecal matters from the intestine, and the 

 products of the excretory and reproductive organs, but also 

 takes an important part in locomotion, the most important 

 movements of the Cuttle-fish, by which it darts rapidly through 

 the water in the direction of the aboral pointed end of the body, 

 being effected by rhythmical contractions of the muscular walls of 

 the mantle-cavity causing jets of water to be forced in the oral 

 direction through the funnel. The free passage of water inwards 

 through the funnel is prevented by the presence in its interior of 

 a flap-like valve opening outwards. The water required for re- 

 spiration and in locomotion is thus drawn in, not through the 

 tunnel, but through the partially-closed slit-like pallial aperture 

 previously referred to. The funnel seems, from the source of the 



