DEVELOPMENT OF THE OVIDUCT IN THE FROG. 275 
is formed from these cells, though whether by involution to 
form a groove, or by proliferation he could not determine. In 
the meantime the groove which formed the ostium of the 
duct, and which was originally dorsal, has become prolonged 
ventrally round the base of the lung. It closes, forming a 
canal, which now opens ventrally. Later this ventral exten- 
sion to some extent atrophies leaving the ostium in a dorsal 
position. 
Marshall and Bles in a paper dealing chiefly with the deve- 
lopment of the Frog’s kidney, published in the second volume 
of the ‘Studies from the Biological Laboratories of the 
Owens College,’ incidentally mention the oviduct. They con- 
firm Hoffmann in his account of the ventral displacement of 
the ostium ; but fail to observe any splitting of the front part 
of the Wolffian duct. They state that the hind end of the 
duct is, in the first year, a solid rod of cells, but fail to notice 
any relation of this rod to the peritoneum. 
My own observations differ from those of Hoffmann in 
several important particulars. It will be convenient to de- 
scribe first the origin and fate of the abdominal opening, and 
then that of the rest of the duct. 
The Abdominal Funnel.—In a tadpole in which the 
hind limbs alone are visible, I find three nephrostomes in the 
head kidney, the cells of which bear long flagella pointing 
inwards, as Hoffmann has pointed out. ‘The first of these is 
situated some way in front of the glomerulus, the second im- 
mediately in front of the attachment of the glomerulus, and 
the third immediately behindit. Before proceeding to describe 
subsequent stages it will be convenient to say a word as to the 
criteria of age employed in the case of these animals. The 
determination of their age is no easy matter ; they vary a good 
deal in size, and just before absorbing their tails are consider- 
_ ably larger than when their metamorphosis is quite complete. 
I have used concurrent measurements of the whole length 
and the length of the tail, and obtained from them indications 
_which are approximately true; but even so one is often disap- 
