1895.J AlfATOMT OF KAUTILUS POMPILIUS. 673 



two moieties. Of these it is only the right with which the sac of 

 Needham communicates, the left being (as will appear later) 

 connected merely with a pecuUar blind sac. The right penial 

 cavity is somewhat semi-pyriform, becoming narrower distally. 

 Its lining is thrown into large smooth glandular-looking rugae, 

 which anastomosing with one another form a kind of raised 

 network with elongated meshes. Outside this lining is the 

 muscular coat about 1-5 mm. thick and largely composed of radial 

 fibres. The muscular layer is traversed by an extensive system of 

 blood-spaces. This is most developed towards the " posterior " 

 end of the penis. It forms a distinct layer near the outer surface 

 of the organ, but its spaces also, though less conspicuously, ramify 

 hither and thither in the general substance of the muscle. 



The left penial cavity is cylindroidal in form, and its diameter 

 only about half that of the right cavity at its widest part. The 

 inner surface of its wall is also thrown into folds ; but these are 

 mainly longitudinal, parallel, and do not anastomose to the same 

 extent as do those of the right cavity. The lining-tissue is of 

 a less deep colour and less glandulai'-looking ; the muscular wall 

 is thinner, and the cavernous layer is also less developed. 



At its " posterior " end, about the level of the point at which 

 the right cavity becomes continuous with the sac of IS'eedham, the 

 left cavity diverges towards the left side, much as the long axis of 

 the Needham's sac does towards the right, and gradually expands 

 into a flask-shaped sac, in this specimen 6 mm. long by 3 mm. 

 broad. This is rounded off and ends blindly. The inner surface 

 of its wall exhibits faint longitudinal corrugations. It is difficult 

 to believe that this left moiety of the penial apparatus does not 

 represent the reduced fellow of the right moiety, i. e., of the 

 right penial cavity plus the sac of Xeedham. On the left side, 

 however, the rudimentary vas deferens does not communicate 

 with the penial sac, but opens, as is well known, directly into the 

 mantle-cavity. The position of this external aperture corresponds 

 very closely to that of the opening of the vas deferens into the 

 spermatophore sac on the opposite side. The whole arrangement 

 strongly suggests that of the functional male genital duct, only that 

 portion from the coelomic aperture to its opening into the sac of 

 Needham represents the primitive duct, and that the Xeedham's 

 sac and the penis are secondarily added structures developed from 

 the adjacent wall of the mantle-cavity. In the young animal, the 

 Needham's sac being not yet expanded, the form and size of the 

 right portion of the apparatus are in almost exactly ^he same 

 condition as is the left in the adult. 



IV. The Buccal Nervous System. 



Lankester ^ says, in speaking of Nautilus : — " No buccal nervous 

 system has been observed in Nautilus ; " and again, " nor has an 

 enteric nervous system been described in this animal." In regard 



' Zoological Articles, p. 142. 



Peoc. Zool. Soc— 1895, No. XLIII. 43 



