214 Edward Phelps Allis jr., 



upward and backward around the anterior end of the gut to fall 

 into ("si uniscono alle") the tw^o lateral dorsal aortae. On p. 448 

 to 450 it is. however, said: that the two mandibular arteries coalesce 

 to form the large median cephalic sinus; that "Piu dorsalmente, il 

 seno si biforca indietro nelle due aorte"; that two short but ample 

 diverticula are sent forward from the sinus, one on either side, and 

 that these diverticula "devono considerarsi come la continuazione 

 delle arterie mandibulare"; and that the diverticulum of either side 

 is continued directly forward as a vessel called by Rafpaele V^. 

 On p. 473 it is further said that while the ventral part of the 

 cephalic sinus represents a continuation of the mandibular arteries, 

 its dorsal portion is a continuation of the "cephalic" aortae; and it 

 is then suggested that the sinus may represent the dorsal ends of 

 a certain number of preoral arches coalesced with each other and 

 also with the related portions of the aortae. Platt (1891) considers 

 the same sinus, in embryos of Acanthias, as a simple anastomosis, 

 or cross-commissure, between the anterior ends of the aortae at the 

 points wiiere they are joined by the mandibular aortic arches; and 

 as this accords wdth the conditions found in the adult, I have so 

 shown it in the accompanying Figs. 7 and 8. 



-iBut, whatever the primitive position of the cephalic sinus, it 

 seems certain, from Raffaele's descriptions, that the lateral aorta 

 of either side, if it is actually continued forward beyond the sinus, 

 must be so continued in the corresponding anterior diverticulum of 

 the sinus, and then probably in Raffaele's vessel Fg; and it is so 

 shown in my diagrams. Raffaele's vessel F,, said by him to arise 

 from the mandibular artery near its dorsal end, then becomes the 

 arteria ophthalmica magna; and as such the corresponding vessel is 

 ■considered by Platt (1891) in Acanthias. V^ would then have the 

 position of a premandibular artery; and the supposition that it may 

 be that artery is in accord with Raffaele's statement (p. 457) that,, 

 in later stages, this vessel assumes colossal proportions, and becomes 

 a ring encircling the optic stalk; much as a choroid gland does. 



In later stages of Torpedo, the anterior diverticula of the cephalic 

 sinus are said to abort, and the blood-current that formerly ran 

 forward through each of them, is then turned downward in the 

 dorsal end of the corresponding mandibular artery and forward in 

 the vessel F^ ; this latter vessel being said to then become the 

 internal carotid. What the course of the blood-current in this artery 

 is after it g-ets to the point where, in younger stages, F^ is joined 



