Prof. Wagner on the Stinging Organs of the Meduse. 83 
dusze swimming in the sea act much more strongly, and even 
the eruptive appearances called Quaddeln are produced, as in 
the case of the Lssera or Urticaria. The pain soon ceases.’ 
It lasted half a-day with one of the party, Dr Will, and, after 
eight days, a redness was still perceptible. 
The internal substance of the body (the so-termed jelly of 
the Medusz) never stings, nor does the inner surface of the 
cavity of the stomach, nor the inner surface of the arms, where 
the pigment spots, the capsules, and the hairs, are awanting. 
At the parts of the skin on which I allowed myself to be stung, 
I always found separated capsules and hairs. It is well known 
that all Medusee do not sting; and, for example, I found no 
power of this kind in the Cassiopea ; and microscopic investiga- 
tion proved the absence of those. capsules and hairs over the 
whole surface of the disc. On the other hand, an Oceania 
(allied to the cacuminaia) stings, but only with the edge 
threads, and in a much smaller degree than the Pelagia. An 
examination shewed the existence of capsules, but of a length- 
ened shape, with long fine threads. But these organs were 
much smaller and finer; they had a remarkable resemblance 
to the structures which I deseribed formerly as Spermatozoa of 
the Actiniz. A new investigation of the Actiniz, as, for ex- 
ample, of the 4ctinia cereus, convinced me that those structures 
formerly described as Spermatozoa are nothing else but sting- 
ing threads of the Meduse ; they stand closely studded round 
the feelers or arms, and on the exterior surface. The threads 
project from long-shaped capsules with that remarkable move-. 
ment which I have elsewhere described, and which I found 
again precisely as formerly. The same organs, but only in 
a different form, occur again in Polypi, as Ehrenberg and Dr 
Erdl (one of my companions) found in the Hydre; and the - 
latter discovered them also in Veretillum. 
It is probable that the stinging has a mechanical and che- 
mical origin ; just as in the majority of what are termed 
poison-organs we find a liquid which collects in a little bladder 
or capsule, and an apparatus capable of doing injury. So it 
is also with many stinging plants, as the Loase@, in which fine 
sharp hairs convey a juice, where circulation can be so beauti- 
fully observed. 
