137 



of the teleosts here under consideration this connection of the efferent 

 mandibular artery with the internal carotid (lateral dorsal aorta) does 

 not exisjt. But in all of these teleosts the dorsal ends of the efferent 

 mandibular arteries of opposite sides are connected by a short cross- 

 commissure, and immediately posterior to this commissure the internal 

 carotids (lateral dorsal aortae) of opposite sides are connected by- 

 anastomosis in the median line; neither of which connections is found 

 in the adult Amia. Of these two anastomoses in teleosts Hochstetter 

 says, on page 93 of vol. 3 of Hertwig's Handbuch der vergleichenden 

 und experimentellen Entwickelungslehre der Wirbeltiere : "Auch bei 

 den Teleostiern bezeichnen wir die Fortsetzungen der dorsalen 

 Aortenwurzeln über die Mündungen der 3 Aortenbogen hinaus als 

 A. carotides intern ae (s. dorsales) ; sie finden ihre Verlängerung in 

 Zweigen, welche das Auge und das Gehirn versorgen. Ursprünglich 

 unabhängig voneinander treten sie später in der Höhe der Mündung 

 der 1. Aortenbogen in der Hypophysengegend durch eine Quer- 

 anastomose in Verbindung miteinander. Diese Anastomose wird dann 

 in der Folge in der Weise gespalten, daß die aus den dorsalen Ab- 

 schnitten der 1. Aortenbogen gebildeten A. efferentes der Pseudo- 

 branchien, welche die zu der Chorioidealdrüse ziehenden A.ophthalmicae 

 magnae abgeben, nunmehr durch eine Queranastomose miteinander in 

 Verbindung stehen, während ihre Verbindung mit den Carotiden zu 

 bestehen aufgehört hat. Dagegen bleiben wieder die Carotiden durch 

 eine vor der Hypophyse gelegene Anastomose dauernd miteinander 

 in Verbindung (Hohen, 1886/87). 



Hochstetter accordingly maintains that the lateral dorsal aortae 

 of teleosts are primarily wholly separate and independent of each 

 other in the mandibular region, not there being connected with each 

 other either by commissure or anastomosis, this opinion being based 

 on Dohrn's descriptions of the conditions found in 11 mm. and 18 mm. 

 larvae of the trout; that is, in what were probably postembryonic 

 conditions of that fish. In young, but postembryonic stages of Amia I 

 (AiLis, 1900) also found this same condition to exist, and in this 

 fish it persists even in the adult. In Acipenser, however, the man- 

 dibular aortic arches are said by Ostroumoff (1907) to be connected 

 at their dorsal ends, during the embryonic period, by a wide anastomosis 

 (sinus cephalicus) which disappears immediately after hatching; and 

 in the youngest stages of Torpedo as yet examined (Raffaele, 1892), 

 this connection or anastomosis of these arteries is also found, and it is 



