10 
J. T. CUNNINGHAM. 
Fishes, such as the eel or the blennies, on Mr. Sedgwick’s 
view we should have a blastopore extending round nine tenths 
of the longest circumference of the body, which seems to me 
a reductio ad absurdum of embryology. Indeed, if, as 
some writers do, we consider the closing of the blastoderm 
over the ventral pole of the yolk as part of the original blasto- 
pore, we have the complete circle, and the blastopore extends 
all round the plane of symmetry. The anterior limit of the 
primitively elongated dorsal blastopore is the infundibulum 
which remains to indicate the position of the original mouth. 
In the preceding number of this Journal Miss Alice Johnson 
speaks of a deep pit at the anterior end of the primitive groove 
in the newt at which epiblast and hypoblast are fused, and she 
believes this pit to correspond in position with the future 
mouth. Anyone who has studied Vertebrate embryos knows 
how very late the actual mouth is in appearing ; it appears 
long after the visceral clefts are wide open and the heart 
beating vigorously. I am convinced that the pit observed by 
Miss Johnson is the commencement of the infundibulum, 
although I cannot speak from actually having traced the origin 
of that structure in the newt. 
All former attempts to find the original mouth ended in 
placing its external opening on the actual dorsal surface, instead 
of on the floor of the anterior cerebral vesicle. Dohrn, before 
he wrote his ‘ Ursprung der Mirbelthiere ’ in 1875, had 
imagined that the primitive oesophagus was represented by the 
pituitary body and pineal gland. In the essay I have men- 
tioned, he abandons this theory for one which made the fourth 
ventricle in the medulla oblongata the rudiment of the 
original mouth. In his address at the British Association 
Meeting in 1881, Sir Richard Owen revived the first hypothesis 
of Dohrn, and stated it as an original discovery. Dohrn has 
recently proved that the hypophysis represents a pair of gill 
clefts. If this be true, the connection of the hypophysis with 
the infundibulum explains itself on my view, because a pair of 
gill clefts might have opened into the mouth. 
Similarly with regard to the primitive anus I cannot accept 
