142 



THE ANATOMY OF VERTEBRATED ANIMALS. 



The kidneys of Teleostean fishes receive a great part of 

 their blood from the caudal vein, wliich ramifies in them. They 

 vary greatly in length, sometimes extending along the whole 

 under-sm^face of the vertebral column, from the head to the 

 termination of the abdomen. The ureters pass into a urinary 

 bladder which opens behind the rectum. 



The brain in the Teleostei has sol- 

 id cerebral hemispheres, and, when 

 viewed from above, the thalamen- 

 cephalon is hidden by the approxima- 

 tion to the hemispheres of the large 

 and hollow optic lobes of the mesen- 

 cephalon, which has a pair of inferior 

 enlargements, lohi inferiores. There 

 is a peculiarity about the structure of 

 the optic lobes, which has given rise 

 to much diversity of interpretation of 

 the parts of the brain in osseous fish- 

 es. The posterior wall of these lobes, 

 where it passes into the cerebellum, or 

 in the region which nearly answers 

 to the valve of Vieussens in mammals, 

 is thrown forward into a deep fold 

 which lies above the crura cerebri, 

 and divides the iter a tertio ad quar- 

 tiim ventriGulum from the ventricle 

 ?h\Trthropufnerves'Tite of the optic lobcs throughout almost 



cerebral hemispheres; C, the the whole extent of the latter. ThlS 

 optic lobes ; A the cerebeUum. ^^^^ . ^ ^^^ ;, ^^^^ . ^ „ ^^ Q.^ttsche. On 



each side of it the floor of the ventricle of the ojDtic lobes is 

 raised up into one or more eminences, which have the same 

 relation to the optic lobes as the corpora striata have to the 

 prosencephalic vesicle. 



The optic nerves simply cross one another, and form no 

 chiasma. The cerebellum is usually large. 



The cephalic part of the sympathetic nerve is present, as 

 in the higher Vertehrata. 



Each of the nasal sacs usually opens externally by two 

 apertures. In some Gymnodonts a solid tentacle is said to 

 take the place of a nasal sac. 



The eyes are abortive in the Blind-fish of the caves of Ken- 

 tucky [Amhhjopus sjjelmus). A fibrous band often passes 

 from the back of the orbit to the sclerotic, and represents the 

 cartilaginous pedicle of the Elasmobranchs. There is no nic- 



FiG. 50 — Brain of the Pike, view- 

 ed from above : A, the olfactory 



