and Urticating Cells. 259 
II. On Urticating Cells in the Gelatinous Mass of the Disk of 
Crambessa mosaica. 
During the histological investigation of this magnificent 
Rhizostomatous Medusa, which sometimes occurs in enormous 
swarms, I came upon some peculiar structures which occur in 
the gelatinous mass of the disk. 
This gelatinous mass is pretty tough, and, in its firm struc- 
ture, resembles the jelly of Cyanea Annaskala*, which has 
been fully described by me. Only here, in accordance with 
the firmer consistency, the fibrillee lie much closer together 
than in Cyanea. The increase in number affects chiefly the 
smooth fibrille. Granular fibres occur particularly well deve- 
loped beneath the olfactory pit. Here they run chiefly verti- 
eally, and therefore pass through the disk-jelly transversely. 
Notwithstanding the probability raised by their position that 
we have here to do with nerve-fibres which unite the sense- 
epithelia of the oral and aboral surfaces of the disk, I am 
not inclined to regard them with any certainty as nerves, as, 
in spite of all my endeavours, I have not succeeded in detect- 
ing any direct connexion with them of the nerve-fibres which 
spread under the sense-epithelia. 
Some of the granular fibres of the jelly beneath the olfac- 
tory pit become thickened at certain points, and contain large, 
long, and narrow urticating capsules, slightly curved into a 
sabre-like form. In the enlargement of the granular fibre, in 
which the urticating capsule les, a nucleus may always be 
- detected ; and consequently the whole is probably to be inter- 
preted as a cnidoblast. I found some of the capsules dis- 
charged ; and in these cases the nettling thread was repeatedly 
bent and imbedded in the granular plasma which surrounds 
the capsule. 
The consistency of the jelly is such that sections may be 
made through it without first hardening it. I was thus en- 
abled to observe these urticating capsules in the living state. 
By the addition of acetic acid they may be at once caused to 
discharge, but the thread remains always in the plasma and 
never issues into the jelly. This seems to indicate that 
between the jelly and the cnidoblast there is a firm separating 
layer, which, however, is not optically perceptible. As with 
the tentacles of Cyanea Annaskala (/. c.), I have tried here 
also whether the urticating capsules discharge themselves 
when no direct irritation affects them, in order to ascertain 
whether a nervous action has anything to do with the discharge 
* Zeitschr. f. wiss. Zool. Bd. xxxviil. p. 472. 
