268 



The Generative Organs of the Oyster. 

 Abstract of a paper by Dr. P. P. C. Hoek.* 



By 

 Gilbert C. Bonrue, M.A., F.I..S., 



With Plates XXII and XXIII. 



. The following description of the reproductive organs of the oyster 

 cannot well be understood without some acquaintance with the 

 general anatomy of the animal. With the help of PL XXII, fig. 1, 

 the most important features of its anatomy may readily be under- 

 stood. It must be remembered that the valves of the oyster^s shell 

 lie right and left of the animal ; that the concave valve which lies 

 undermost in the natural position of the animal is the left valve, and 

 the flat upper valve is the right valve. The hinge marks the dorsal 

 border of the animal, and the opposite border is the ventral border. 

 That side which is on the observer's right in fig. 1 is the anterior 

 surface, and that on the left hand is the posterior surface. As the 

 animal is compressed from side to side the anterior and posterior 

 surfaces are very narrow. The great adductor muscle, by which the 

 valves of the shell are closed, is seen lying in the centre of the 

 animal in fig. 1. 



If the right mantle lobe is cut through along the anterior and 

 ventral border of the adductor muscle, as in the figure, a finger- 

 shaped process, called by Dr. Hoek the 07rd process, is seen to pro- 

 ject from the trunk of the oyster, and to lie closely applied to the 

 ventral border of the muscle. This oral process contains a loop of 

 the intestine and, in addition, a portion of the reproductive organs 

 and of the excretory organ. A large nerve-ganglion, the branchial 

 ganglion, lies between the adductor muscle and the oral process. 

 From this ganglion a number of nerves are given off, the most cou- 



* Tijdschrift der Nederlandsche Dierkuudige Vereeniging, Supplement Deel i, Aflever- 

 ing i, p. 115. Leiden, 1883. See also Dr. Hoek's prize essay iu the Literature of the 

 International Fisheries Exhibition. London : Win. Clowes and Son. 



