XX] GENITAL ORGANS 463 



on the inner side of the kidney to form the spacious posterior 

 cardinal sinuses, as the front portions of the posterior cardinals are 

 named. These two sinuses lying ventrally to the kidneys partly 

 coalesce. Each sinus curves forwards and outwards to join the 

 ductus Cuvieri and at this point it is met by the so-called sub- 

 clavian vein which returns blood from the region of the shoulder 1 . 

 The pelvic vein receives the blood from the side of the cloaca by the 

 cloacal vein and the blood from the pelvic fin by the femoral vein. 

 It then opens into a longitudinal trunk, called the lateral vein, 

 which runs along the side of the body beneath but parallel to the 

 posterior cardinal vein. The lateral vein in front receives the brachial 

 vein from the ventral side of the pectoral fin (not to be confounded 

 with the subclavian from the dorsal region of the pectoral girdle) and 

 then opens into the ductus Cuvieri. The cloacal veins further give 

 off median branches which unite and then distribute blood to the 

 viscera, so that some blood from the pelvic fin may also return to 

 the heart through a portal system. 



The ovary is a single ridge of the dorsal coelomic wall, its 

 fellow which is indicated in the embryo having dwindled and dis- 

 appeared ; the oviducts are long and united far in front so as to open 

 by a common internal opening, situated ventral to the liver (Fig. 

 226). In the middle of its length each oviduct has an enlargement 

 caused by a thickening of its walls due to the development of gland 

 cells. This is called the oviducal gland, and its function is to 

 secrete the pillow-shaped elastic egg-shell. The egg is large and 

 well charged with yolk. The oviducts unite posteriorly to open 

 into the proctodaeum or cloaca behind the anus. There are 

 two large testes, and these are united anteriorly and connected 

 to the front end of each of the kidneys, which extend along the 

 entire length of the abdominal coelom. The anterior region of 

 the kidney or mesonephros (for no pronephros is developed) is 

 narrow and its excretory function has almost disappeared. The 

 testis is connected with the front end of the mesonephros by vasa 

 efferentia. These vasa efferentia eventually open into a single 

 coiled duct. This duct is the archinephric duct which has also 

 lost its original function and become a vas deferens; it lies on the 

 ventral surface of the kidney and conveys spermatozoa from the 

 mesonephros to the cloaca. It enlarges at its hinder end into a 

 vesicula seminalis. The posterior and functional part of the 



1 This vein has been described as receiving blood from the pectoral fin, but 

 O'Donoghue has shown that this is a mistake, and that its blood is derived 

 solely from the region of the shoulder. 



