106 GEGENBAUR, ON MEDUS&. 
higher Medusze, there is a communication between the 
marginal vesicle and the gastro-vascular system, a fact dis- 
puted by Kélliker. The interior of the vesicle, like that of 
the canal, of which it is, as it were, a derivation, is lned 
with a very delicate ciliary investment, by means of which a 
constant circulation of the contained fluid is maintained. 
Kolliker and others have described an opening on the upper 
side of each marginal vesicle, through which the ampulla 
above described would communicate with the surrounding 
medium; but Gegenbaur denies altogether the existence of 
any openings of the kind. 
At the free end of the marginal body, and constituting 
nearly its whole apex, is placed an oval sacculus, 0°14’ long 
by 0:09’ broad, closely filled with prismatic crystals, and 
which probably represents the most important physiological 
portion of the organ. The membrane of this sacculus is 
indeed thin, though possessing a certain resistance. At the 
sides and distal end it is enclosed by the walls of the marginal 
body itself, which are here somewhat thinned, whilst the 
part corresponding to the ampulla is covered with the ciliary 
lining of the latter. There is no communication between the 
ampulla and the crystalline sacculus. Gegenbaur has never 
perceived any movement in the crystals, and denies the 
existence of cilia in the sacculus containing them. The 
crystals themselves are six-sided prisms, obliquely truncated 
at each end; in length and number they vary very much. 
The longest measure 0:02'". They appear to be insoluble in 
acetic acid. 
Gegenbaur then proceeds to describe the unusual forms of 
marginal bodies which exist in species termed by him 
Ephyropsis,* and probably belonging to the genus Nausitho, 
of Kolliker,+ and in Carybdea marsupialis, in both of which 
Meduse, moreover, the ocelli contain sperical, refractive 
bodies. 
After discussing the question concerning the function of 
these bodies, Gegenbaur inclines to the opinion, that the 
coloured spots, especially when furnished with a spherical 
refractive corpuscle, are of the nature of visual organs, whilst 
he throws out the supposition that the other kind may be 
excretory. Relying chiefly upon the absence of motility in 
the concretions or crystals, and of cilia in the cavities in 
which these bodies are lodged, he attempts to show the im- 
probability of their being auditory organs. 
* “Comptes rendus,’ t. xxxviii. 
+ ‘Zeits. f. Wiss. Zool.,’ Bd. iv, p. 323. 
