THE ANIMAL CLIMAX-THE CHORDATES 



293 



external nares 



olfactory bulb 

 cerebrum 

 optic lobe 

 cerebellum, 



rnedulla 



spinal 

 rd- 



mouth 

 external nares 



eye 



pbonynx 

 qill 



truncus arteriosus 



auricle 



ventricle 



sinus veoosus 



pericardiol chamber 



liver 



qall bladder 



bile duct 



pectoral tin 



pyloric caecum 

 Stomach 



pancreas 



spleen 



pelvic fin 



operculuo) 



intestine 



njesentery 

 fat 



testis 

 anus 



uroqenital pore 

 urinary bladder 



dorsal fin 



anal fin 

 lateral line. 



caudal fin. 



internal anatomy dorsal external view 



F!g. 13-17. Teleost fish in longitudinal section and dorsal view. 



extinct until a fisherman off the coast of 

 South Africa hauled one in (Latimeria) in 

 1939. Unfortunately the true value of the 

 find was not discovered until the body was 

 destroyed, although the skin was mounted 

 (Fig. 13-18). Relatives of the "lobe-finned" 

 fish are not uncommon today. The lungfish, 

 for example, inhabits certain tropical parts 



of the earth where frequent droughts occur. 

 Since this form followed a different path of 

 evolution, it does not possess well-devel- 

 oped appendages and, in spite of the fact 

 that it has lungs, probably did not give 

 rise to the land forms. 



One other absolute essential had to be 

 achieved if fish were to live outside of 



