MOLLUSC A. 49 



indicated by a black bristle. The nerve-collar (through which 

 a black bristle has been passed) encircles the oesophagus. From 

 the supra- cesophageal portion delicate nerves pass forwards to 

 supply the tentacles, lips, &c. A little to the left of the left 

 salivary duct may be seen the left parietal nerve, double at 

 its termination, passing from its origin in the parieto-splanchnic 

 ganglion to its peripheral distribution in the body-walls. Be- 

 tween the left salivary duct and the stomach the central 

 portions of three other nerves may be seen in connection with 

 the same ganglia, viz. the two parietal nerves of the right side 

 and the great visceral nerve in connection with the aorta. The 

 second black bristle (the lower one) is inserted into the anterior 

 aorta, which passes through a foramen between the upper or 

 parieto-splanchnic, and the lower or pedal portion of the sub- 

 cesophageal mass. 



On the left of the preparation is the pulmonary sac. The 

 greater portion of its diaphragm-like floor has been removed, 

 and its highly vascular roof exposed. At the lower edge of 

 the sac, and on the right side of it, is the bilocular heart. 

 To the left of the heart is the pale triangular kidney. 



The hermaphrodite gland is lodged in the concavity of the 

 penultimate and ante-penultimate coils of the liver, which 

 occupy the lowest part of the preparation. From this gland 

 a convoluted hermaphrodite duct passes upwards to a tongue- 

 shaped body, the albumin iparous gland; and after this junction 

 the duct passes upwards again as a thicker and much plicated 

 tube, having closely applied along it a ribbon-like glandular 

 prostatic mass. At about the level of the animal's head this 

 hermaphrodite duct divides into the oviduct and the vas defe- 

 rens. The vas deferens passes forwards and joins the base of 

 the penis at the point where the long whip-like flagellum also 

 joins it. On the extreme right of the preparation is the globular 

 spermatheca with its duct leading to the oviduct into which it 

 opens. Connected with the vagina is the 'dart sac,' and 

 between the latter and the oviduct are seen the 'multifid 

 vesicles.' 



The external generative opening is on the right side of the 

 animal at the base of the right superior tentacle. 



CT, * 



