rm 



CHORD AT A. 



liulbus {< ') is 'A nmscular swelling in front of the conus, in the 

 .-irterial trunk. 



Tliu connexion of ventral iind dorsal aortie is effected in young 

 lishes (fig. •"i!)';) by tlie gill ai'teries directly; later by means of the 

 cuniplicated loo])s of the gill circulation. When these are de- 



FiG. 536,— Forms of hearts of fishes in schematic lone section. (After Boas.) .4. sela- 

 chian and most ganoids: *. AmUi; ('. Teleost, <i. auricle: h. bulhus arteriosus: > . conus 

 arteriosus; A-, valves; s, sinus venosus; t, truncus aortffi; v, ventricle. 



YlG. .597.— Head of embryo teleost {r>iae:ram from (Tegenbaur. i k, auricle; (//-r. ventral 

 aorta \\ith arterial arches; <id, dorsalaorta ; c, carotid ; <lc. Cuvieriau duet, formed b.v 

 union of jugular and posterior cardinal veins ; n, nostr il : >■, ^nll clefts : .^r. sinus veno- 

 sus; c, ventricle. 



veloped, afferent branchial arteries, gill capillaries, and efferent 

 arteries can he recognized, the latter uniting to form the dorsal 

 aorta and also giving oft' the arteries (carotids), which go to the 

 head. 



The nc)i]iridia arc a pair <if hirgc reddi,sh-br<.>wn organs lyinsj 

 outside tli(^ body cavity to tin' rigid and left of The vertebral 

 lolnnin, usually extending from heart to anus. Their duets empty 

 behind tlie anus or in the dorsal wall tif the intestine and are often 

 provided witli enlargements called, from their functions, urinary 

 liladders, tdthough totally different morphologically from the 

 urinary bbidder of the liighcr vertebrates. The gonads, suspended 



