194 J. GRAHAM KERR. 



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 Needhara. On the left 

 side, however, the rudimentary vas deferens does not communi- 

 cate 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 spermatojihore 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 Needham'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 the 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 

 auimal." In regard to both these statements. Professor Lan- 

 kester seems to be in error, as a complicated buccal system was 

 described and figured by H. v. Jhering^, while at least part of 

 an enteric system was described by Keferstein*. In regard to 

 the buccal nervous system it seems advisable to give a short 



1 Zoological Articles, p. 142. 



2 Vergl. Anat. des Nervcnsystcms der MoUuslien, p. 2G3. 

 ' Bronn's Thicneich, Malacozoa, p. 1373. 



