SIGNIFICANCE OF EUPFFEE’s VESICLE. 
3 
to hatch out on August 21st, the eighth day, and continued 
hatching on the following day. I next obtained eggs at 4 a.m., 
on August 26th ; the temperature was about the same as before, 
and hatching took place on the eighth day. 
As will be seen from fig. 1, Kupffer’s vesicle is seen on the 
third day in the herring, by which time the eyes have appeared 
and the two ends of the embryo almost meet at the ventral 
pole of the yolk. 
Historical. — Kupffer’s vesicle was originally discovered 
and described by Kupffer 1 in 1868, in the embryos of Gaster- 
osteus aculeatus, Gobius minutus, and Gobius niger. 
He named it “ the allantois” without considering very carefully 
whether its relations corresponded to those of the allantois in 
the Amniota. In subsequent papers he has come to the con- 
clusion that the vesicle is closely connected with the formation 
of the urinary ducts. Balfour in his * Comparative Embry- 
ology,’ states that Kupffer’s vesicle is the representative ol 
the post-anal vesicle in Elasmobranchs, without discussing the 
reasons which led him to this view. Kingsley and Conn 2 in 
1883 described the origin of Kupffer’s vesicle in Ctenolabrus. 
Their figures and descriptions are scanty, and refer only to 
optical sections. It is stated to arise from a number of small 
granules which fuse together ; it is probable that these granules 
are small spaces between the periblast and hypoblast, and it 
makes no difference to my account of the vesicle whether it 
arises as a single space or from a number. 
In a very recent paper by A. Agassiz and C. C. Whitman, 3 
the following remarks are made concerning Kupffer’s vesicle : 
“ Although we have been able to trace the entire history of 
Kupffer’s vesicle in several species of ova, its significance 
remains as complete a puzzle as ever. Kingsley and Conn 
were the first to give an accurate account of the origin of this 
vesicle, 4 but they give us no information in regard to its 
1 * Arch. f. mik. Anat.,’ Bd. iv. 
2 ‘Memoirs of Boston Soc. of Nat. Hist.’ 
3 ‘Proc. Amer. Acad, of Arts and Sciences,’ vol. xx, Aug., 1884. 
4 This remark is not altogether impartial — the vesicle is not correctly 
