IS8 ON THE MORPHOLOGY OF THE CEPHALOUS MOLLUSCA 



•of the former portion, and almost reminds one of the sculptor's vine- 

 leaf 



The Testis is not very easily to be distinguished from the liver, be- 

 hind which it is placed, until the contained spermatozoa are recognized. 

 It occupies about the posterior half of the nucleus. There is hardly 

 any proper vas deferens, but the testis opens by a very short canal at 

 the base of the penis. 



The Ovarium (o) occupies a position similar to that of the testis 

 (figs. 2 and 3). A wide oviduct arises from it about its centre, on the 

 right side, and after making one bend, passes downwards, and opens 

 close to the base of the metapodium. 



The ovarian ova were oval, about -^-i^dth of an inch in diameter, 

 with a clear, delicate, germinal vesicle about ^^dth of an inch in 

 diameter, and a pale, circular, clear, but thick-walled vesicular ger- 

 minal spot about j-Joij^dth of an inch in diameter. In the oviduct the 

 ova possessed either an entire granular yelk, in which I could not 

 detect any germinal vesicle, or the yelk was broken up into two or 

 more (but not many) spherical or subspherical masses, containing a 

 clear vesicle, the embryo-cell. 



In some individuals a long tube (figs. 2 and 5), half as long as the 

 body or more, depended from the orifice of the oviduct. It was 

 colourless and transparent, and appeared as if articulated from its 

 membrane being thrown into regular annular folds. 



This egg-tube contained a double series of ova, in which the yelks 

 had undergone division into 8 to 15 masses of very variable size. 

 The ova seemed to have become more divided the nearer they were 

 to the distal extremity of the tube, but I could find none containing a 

 distinct embryo. 



Tlie Nervous System (figs. 6 and 7). — Two three-lobed ganglia, 

 closely applied together by their inner edges (fig. 7), are placed be- 

 tween the eyes. Each gives off several branches to the parietes and 

 the following important trunks : — 



I. A long branch forwards, which terminates in a small ganglion 

 (/9) placed in the angle of union of the cesophagus with the buccal 

 mass, and joined to its fellow by a very short commissure beneath the 

 <esophagus. From these " buccal ganglia " various small nerves are 

 given off forwards to the buccal mass and parts about the mouth, and 

 backwards, to the oesophagus. 



^ According to Milne-Edwards (Sur divers Molliisques, Annales des Sciences, 1842), a 

 perfectly similar penis is found in Carinaria. Pie states, however, that the vas deferens 

 traverses one portion of this organ, which is certainly not the case in either Firoldides or 

 Atlanta. 



