96 SUPPLEMENT ON 



in bags, but in a collection of leaflets. No canal is visible, 

 and the spawn can escape only by dropping into the abdomen, 

 and thence passing out through one of the two openings at the 

 side of the vent. This at least is believed of the lamprey, 

 and conjectured to be the case with eels. Even trout is 

 asserted to be in the same condition, for the ovaries are closed 

 on the side of the abdominal cavity, and what might be taken 

 for the oviduct is reduced to a simple ligament. The number 

 of roe eggs contained in prolific species is sometimes prodi- 

 gious, amounting in several to hundreds of thousands. 



There are found occasionally individual fishes, who have 

 on one side an ovary, and on the other a milt, or testiculus, 

 and who therefore are true hermaphrodites. It seems even 

 that certain species naturally unite the organs of both sexes. 

 Cavolini asserts this to be the case in a serranus, and Sir 

 Everard Home in both eels and lampreys. 



Rays and squali have these organs more complicated. The 

 testicles of rays, placed upon the stomach, towards the summit 

 of the abdomen, are composed of lobes harder and rounder, 

 and of a part that is soft, and more like the milt of ordinary 

 fishes : in squali they form large cylinders, coiled in a vermi- 

 form manner, and internally divided into an infinity of small 

 vessels. From their summits arise two epididymi, each com- 

 posed with many folds of a single vas deferens, becoming 

 smaller and less tortuous as it approaches the vent : after 

 swelling into a kind of seminal vesicle, it opens along with 

 that of the other side into a conical prominence of the supe- 

 rior side of the rectum, near the vent. The females are 

 provided with two ovaries, where the yolks of the spawn grow 

 as in poultry ; those that escape are received by the fun- 

 nels of the two oviducts opening above the liver near the 

 diaphragm. These oviducts are membranous at first, and 

 traverse a gland of a particular tissue, shaped like a kidney, 

 which it seems secretes the horny substance of the shell ; after 



