4 
J. T. CUNNINGHAM. 
subsequent history, and almost no details of its origin and 
growth. As they have stated the vesicle arises by the fusion 
or confluence of a cluster of granules. Those granules are 
at first few in number (2 — 4) more or less angular, quite dark, 
and not more than '002 mm. in diameter. In general appear- 
ance they are not distinguishable from the scattered granules 
seen in other parts of the ovum. In Ctenolabrus they appear 
soon after the embryonic rim passes the equator. They 
increase in number, grow larger, coalesce by degrees, and 
finally blend into a single bubble-like vesicle in the course of 
five hours. This vesicle, - 01 mm. in diameter or more, more 
than doubles its diameter in the next hour and a half, and 
steadily expanding attains its maximum dimensions at the time 
the blastopore closes. During all this time it lies beneath the 
chorda and the entodermic stratum and has no sort of relation 
with any tubular structure whatever. As the alimentary 
canal is not yet in existence it is difficult to see how this 
vesicle can be the homologue of a dilatation which arises in 
and has no sort of existence outside of the post-anal gut. 
Ventrally and laterally it is bounded by periblastic material, 
but it has no cellular envelope in the strict sense of the 
words.” 
The authors then go on to describe the final history of the 
vesicle. Their description is not quite clear, but the meaning 
seems to be that the hypoblast above the vesicle is hollowed 
out to form a longitudinal furrow which deepens until a closed 
canal, the lumen of the gut, is formed, the depression in the 
periblast disappearing in the process. The authors think it 
probable that there exists from this time onward a lumen in 
the portion of the gut thus formed. 
Agassiz and Whitman give no figures of the vesicle nor do 
they state if they confirmed their results by the examination of 
sections. Their paper has for its chief object to announce the 
important discovery that the nuclei of the periblast are origi- 
described when it is said to originate from globules, and Kingsley and Conn 
do not even point out its relation to the germinal layers. 
