SUMNER: KUPFFER'S VESICLE 



75 



the egg of the " Stone Cat " (Notu.rus) although entirely lacking in the closely re- 

 lated Amiurus. It appears a little earlier than Kupffer's Vesicle and attains a 

 somewhat greater size (see figure 34). This " yolk vesicle " is surrounded by a com- 

 plete wall of periblast, except on the upper side, where it is bounded directly by 

 the cells of the embryo. There is at no time any connection between the two. 



EIGENMANN ('92) describes in the case of Cymatogasler a single large vesicle lying 

 partly in the yolk and partly in the embryo. This latter subdivides into three por- 

 tions : a lower one, which he calls the "yolk vesicle" ; an intermediate portion, 

 which he homologizes with the post-anal-gut, and an upper cavity, which he con- 

 siders to be the equivalent of the neurenteric canal. KINGSLEY and CONN ('83) orig- 

 inally described Kupffer's Vesicle in Ctcnolabras as arising by the fusion of a mass 



FIGURE 33. 



FIGURE 34. 



Kv 



Section through posterior end of same embryo as that 

 in figure 20 (camera lucida). Kupffer's Vesicle (Kv) is 

 beginning to make its appearance aa a group of small 

 vesicles. 



Transverse section through embryo of Noturus, showing 

 fully developed Kupffer's Vesicle and yolk vesicle. A 

 layer of pavement cells, continuous with the gut-hypo- 

 blast, is here seen to underly the columnar epithelium 

 forming the lower wall of Kupffer's Vesicle. This 

 pavement layer has probably reached its present position 

 by growing in from the sides, as it is not present in an 

 earlier stage (figure 33). 



of vacuoles in the yolk, and^this account has been confirmed by several subsequent 

 workers on pelagic eggs (e. g., AGASSIZ and WHITMAN, see p. 52, ante). The dorsal 

 cellular wall of the vesicle becomes differentiated above this resulting single vacuole. 

 HENNEGUY ('88) states that there frequently occurs beneath the posterior end of the 

 trout embryo a. vesicle in the yolk. In the case of Salvelinus the whole periblast is 

 much vacuolated, but in some specimens I have found a particularly large vacuole 

 lying in the appropriate position. AGASSIZ and WHITMAN have described certain 

 "secondary caudal vesicles" probably of a similar nature. M'!NTOSH and PRINCE 

 ('90) speak of a "multiplicity of vesicles" in the gurnard and some other fishes. 

 EYCLESHYMER ('95) describes two such accessory vesicles in Lophius, one of which 

 communicates at one period with Kupffer's Vesicle. 



