Albert C. Eycleshymer and James Meredith Wilson 153 
dicated for some time by the large coarsely granular cells which lined it. 
The anus arises through an invagination just behind the line of closure 
of the blastopore and soon becomes continuous with the appendicular 
gut. The portion posterior to this or the post-anal gut proper soon shows 
retrogressive changes. The walls lose their distinctive hypoblastic char- 
acter, the lumen becomes obliterated and the entire structure later disap- 
pears, playing no part in the formation of later embryo. 
Kupffer’s vesicle has been studied previously in Amia by Dean, 96, and 
Sumner, ’oo. Dean writes as follows: “The ecelenteron, now a deep 
cavity beneath the dorsal lip, extends forward below the entire head ; its 
hinder dilation immediately below the dorsal lip is to be interpreted as 
representing Kupffer’s vesicle.” Regarding Dean’s interpretation Sum- 
ner says: “ Dean maintained that this cavity simply represented the 
angle formed by the blastoderm’s margin, as it was mechanically turned 
in upon itself during its circumcrescence of the yolk. This simple me- 
chanical explanation I cannot accept for the teleosts because (among 
other reasons) the vesicle in some fishes is not formed until the blasto- 
derm has nearly or quite finished its journey over the yolk and thus the 
supposed mechanical cause no longer exists.” In considering the func- 
tion of this structure in fishes Sumner further says: “It has for some 
time been my view that this vesicle contains a more fluid yolk, partly 
assimilated through the activity of the periblast and intended for the 
nourishment of the growing embryo. I have also expressed the view that 
Kupffer’s vesicle represents an embryonic digestive organ (more properly 
an organ of absorption).” 
In considering this structure it is necessary to recall what has been 
said regarding the periblast in the teleosts, ganoids, and amphibia. 
While the roof of the vesicle in all these forms is the same, the floor in 
the teleosts is sometimes of periblast and again there is a cellular floor 
lying upon the periblast.. These facts are at first difficult to interpret, 
yet if as H. V. Wilson, g1, suggests the latter condition is to be regarded 
as secondary, the difficulties are in a measure overcome. If it be ac- 
cepted that the floor of Kupfer’s vesicle is periblast in the teleost and that 
the periblast of Lepidosteus is the homologue of that of the teleost 
Eycleshymer, 03, we are placed in position to say that the ventral wall 
of the vesicle in Amia, Acipenser and the amphibia is represented by 
nothing more or less than the gastral floor. The vesicle then represents 
the posterior portion of the primitive digestive tract. This being the 
case in Amia no one need hesitate to accept Sumner’s view that the 
vesicle may have had a digestive function. 
The first description of the growth of the adhesive organs is given by 
la 
