208 SUB-CLASS (AND ORDER) TELEOSTEI. 



(ef) anastomoses with its fellow of the opposite side and then 

 passes round the external carotid to the choroid gland, a rete 

 mirabile in the choroid coat round the entrance of the optic nerve 

 into the eye. When the pseudobranch is not present, there is 

 no choroid gland. In Gymnarchus the efferent vessels of the 

 third and fourth branchial arches do not join the dorsal aorta 

 but pass to the air-bladder. 



The blood of the choroid gland supplies the choroid coat. The iris 

 and sclerotic are supplied by the external carotid. The efferent bran- 

 chial vessels give off small vessels for the nutrition of the branchial arch 

 tissues, and near their ventral ends they give off vessels for the ventra 

 part of the body, the neighbouring parts of the head, and even in some 

 cases the heart. The hyoidean artery which supplies the pseudobranch 

 is an example of this system of arteries. 



The dorsal aorta is frequently closely adherent to the ventral wall of 

 the vertebral column, so that the latter appears to form part of its wall. 

 It may be swollen at intervals, and in some forms (Esox, Clupea, Salmo, 

 Silurus, etc.) a fibrous elastic band projects into its cavity. The principal 

 branches are subclavian, which may come off from the circulus cephalicus, 

 the coeliaco-mesenteric which frequently gives off the air-bladder vessel 

 and a posterior mesenteric. 



The veins are arranged in the usual piscine fashion. The left 

 posterior cardinal is often smaller than the right and appears as 

 a small branch of the latter coming from the anterior part of the 

 kidney ; or the right vein may alone be present, lying almost in 

 the middle line and receiving branchlets from each side. A 

 renal-portal system appears to be present in most Teleosteans. 

 The hepatic-portal vein may receive tributaries from the air- 

 bladder, the gonads (Perca, Bhnnius, Cyprinus, Osmerus, etc.), 

 and the ventral body wall (Salmo, Alosa, Clupea, etc.), though 

 these veins more generally open into the posterior cardinals. 



The body-cavity has the usual piscine arrangement. The 

 pericardium is completely separated from the general body- 

 cavity. Paired abdominal pores opening at the sides of the 

 anus are absent in most Teleosteans, but they are found in the 

 Salmonidae and Mormyridae, though not universally. They 

 must not be confused with the pore-like oviducts of female 

 Salmonidae, etc. (see below). 



The urinary organs are paired streaks of kidney substance 



* M. Weber, Morph. Jahrbuch, 12, 1886, p. 336. Jungersen, Arb. a, d. 

 Zool. Inst. Wurzburg, 9, p. 93. 



