262 Dr. R. von Lendenfeld on Guard-Polyps 
or other exists in these animals which is in connexion with 
the nervous system of the animal, and the action of which — 
consists in its exerting, under certain conditions, a pressure — 
upon the urticating capsule. Such a mechanism might exist — 
either within the enidoblast or outside it. 
T believe that the former is the case, and support my 
opinion upon three facts. 
In the first place we have before us in the cnidocil a struc- — 
ture which is evidently connected with the mechanism of dis- 
charge, just in the same way as the nervous system of the — 
animal, because, under certain conditions, a touching of the — 
enidocil suffices to burst the capsules, just like an impulse of 
the will of the animal. But it is precisely the plasma-enve- 
lope of the urticating capsule in which both the enidocil and 
the pedicle open, and thus at this place alone we shall pro- 
bably have to seek the mechanism which can be set in motion 
from both sides. 4 
It is indeed not impossible that the irritation of the enidocil — 
in fact comes as sensation to the knowledge of the subepi- 
thelial ganglion-cells, and that then only is some other 
mechanism for the discharge of the urticating capsules set — 
in motion from this point. But this appears to me extremely — 
improbable. 
In the second place the urticating capsules in the disk of 
Crambessa mosaica discharge themselves upon nervous irri- 
tation; and it can scarcely be supposed that the irritations 
cause the contraction of the jelly in the vicinity of the enido- — 
blasts, but rather that they superinduce a discharging action in © 
the plasma of the cnidoblasts itself. 
Thirdly, we must here cite the noteworthy discovery of — 
Chun *, who has detected in the plasma-envelope of the urti- — 
cating capsules of Physalia a network of contractile fibres, by 
the contraction of which a rupture of the capsule can be easily — 
effected. Here, in an animal celebrated for its urticating 
qualities, we find the plasma of the cnidoblasts of a higher — 
erade; it has already secreted muscular fibres. 
Considering these points, I would assume the contraction of © 
the plasma-envelope to be the cause of the discharge of the 
urticating capsules, and not a contraction of the pedicle. | 
I have postponed the discussion of the centripetal extre= 
mities of the pedicles of the urticating capsules of the guard-— 
animals described in § I. until now, because it may be of © 
more general importance. Although I am not sure, the im-_ 
pression has been made upon me that the pedicles, as stated 
* Zoologischer Anzeiger, Bd. iv. p. 646. 
