424 



PISCES. 



cavity opens externally, almost within the verge of the anus, in a pro- 

 jecting part like a kind of nipple. 



Of the Female Parts, or Ovaria. — The ovaria are placed almost all 

 along the hack, in the centre of the abdomen, from the liver above, to 

 near the lower part of the abdomen, the lower end lying between the 

 two kidneys. They are attached to the back through their whole 

 length by a doubling of the peritoneum, receiving their vessels at this 

 attachment between this doubling. From this one attachment go off 

 the two ovaria, as if dividing into two lamellae, but which join one 

 another across at their common union. Each ovarian lamella is made 

 up of, or divides at its edge into, a number of processes which float 

 loose in the abdomen. They are composed of two transparent mem- 

 branes, which may be called doublings of the peritoneum, united at a 

 little distance by a number of partitions, which form cells in the inter- 

 stices between the two. That part of the external membrane which 

 covers each cell has a whitish speck or body in it, and which seems to 

 have a dent in its centre. These bodies I suspect are the nidi of the 

 ova. The ova are formed on the inside of this doubling of the mem- 

 brane which composes the ovarium ; probably one in each cell. This 

 circumstance of the formation of the ova on the inside of the ovaria is 

 somewhat similar to the formation of the ova in the frog and toad. As 

 the cavities or cells of the ovaria do not communicate, or open, exter- 

 nally, as in fish in common, and as there are no proper oviducts as in 

 the ray-kind, it is at first view difficult to account for the mode of 

 propagation or the mode of exit of the eggs. 



It would appear from every circumstance that the coat of the cell of 

 the ovarium opens as in the frog and toad, and that the egg passes 

 through it into the general cavity of the abdomen, being there perfectly 

 detached. [In Batrachia the ova are received into oviducts, but, in the 

 lampreys,] by certain operations of the abdominal muscles they are 

 worked towards the anus, and are at last squeezed out by the passages 

 wbich lead from the abdomen into the common passage of the two 

 ureters before mentioned, and then they are thrown out at the nipple 

 [valvular outlet of peritoneal canal]. In one fish there were several 

 ova lying loose in the cavity of the abdomen; and, by handling the 

 ovaria which had some of tbose eggs in their cells, the eggs readily 

 made their escape. The eggs are round bodies, flattened on the two 

 opposite sides \ I never saw any thing like a stone in any of the 

 cavities of a fish. 



1 [Hunt. Prep. Phys. Series, Nos. 2658, 2659, 3196, 3197, 3198, 3199, 3200, 

 3201. See also vol. i. p. 218.] 



