124 



JOHN LEWIS BREMER 



Ar. 2. 



. 1 1: 3. 



Con. Art. 



Ar.4. 



Fig. s Rabbit, LO days, 23 segments, 3.2mm., H.E.C.j-no. 940. Reconstruc- 

 tion (if t he lil (Hid -vessels of 1 he head end of the embryo, seen from the ventral side ; 

 t he heart removed by cutl ing through the conus arteriosus. Lettering same as in 

 fig. ."), and also Ar.l. Ar.2, Ar.3, Ar.4, aortic arches; E.C., external carotid arte- 

 ries, cut; x and //, remains of second channel for sec 1 aortic arch. X 125. 



the fourth arch and from the dorsal aorta sprouts arise, at first 

 in part solid, which curve around the pharynx and, entering the 

 same sheet of mesoderm in which the ventral aorta lies, form there, 



