xn 



PHYLUM MOLLUSCA 



751 



cylindrical cells provided at their free extremities with short cilia, 

 and produced at their bases into processes continuous with nerve- 

 fibres derived from the statocyst-nerve. Enclosed in the cavity 

 of the statocyst and attached to the macula is a large statolith 

 (Fig. 678) of dense composition and complicated form. The 

 function of the statocysts as organs of hearing is quite unproved ; 

 it has been shown by experiment that their removal leads to a loss 

 of the power of co-ordinating the movements in such a way as to 

 maintain the equilibrium. 



v.cav 



jnecL.s 



s.f 



FIG. 679. Sepia officinalis, excretory organs. W. w. abdominal vein ; ap. 1, funnel-like 

 opening from the pericardium ; ap. 2, aperture of communication between the left and the 

 median renal sac ; br. ht. branchial heart ; ink. s. t>. ink-sac vein ; med. s. median sac ; 

 pall. t>. pallial vein ; ur. renal aperture (ureter) ; v. caw. vena cava ; ven. app. venous 

 appendages of the afferent branchial veins. (From Vogt and Jung, after Grobben.) 



Supposed to be olfactory in function is a pair of ciliated pits, 

 which open by slits on the surface behind each eye ; among the 

 ciliated cells lining the pit are numerous narrow sensory cells con- 

 nected at their bases with the fibres of a nerve derived from a 

 small ganglion situated close to the optic ganglion. A small eleva- 

 tion (Fig. 669, gust), covered with papillae, on the floor of the buccal 

 cavity just in front of the odontophore, is perhaps an organ of taste. 



The excretory organs or kidneys of Sepia (Figs. 679 and 

 680) are a pair of thin-walled sacs, which open into the mantle- 



3 B 2 



