LIMNOCNIDA TANGANICiE. 
85 
in Limnocnida, in spite of the completeness of Gunther's 
account. 
I desire to take this opportunity of thanking Dr. Harmer 
and Mr. Kirkpatrick for their assistance in obtaining material 
for examination; my thanks are also due to Mr. R. T. Gunther, 
of Magdalen College, Oxford, who very kindly read through 
parts of my manuscript. 
The work in connection with this paper was carried out in 
the Zoological Department of the University of Birmingham. 
2. The Structure and Function of the “ Nettle-Ring." 
The nettle-ring, or thickened band, containing stinging- 
cells, which occurs at the edge of the umbrella, is a very 
characteristic feature of the anatomy of Limnocnida. The 
minute structure of this organ was described by Gunther as 
being similar to that of the peronium of other medusae, and 
as consisting of modified stinging-cells. He considered its 
function as possibly skeletal as well as defensive. 
In a recent paper published in this Journal (5) I 
endeavoured to show that the bulbous swellings which are 
so constantly present at the bases of the tentacles of 
Craspedote medusae have a definite function besides that 
of bearing the ocellar sense-organs, serving to develop and 
store up the stinging-cells of the tentacle batteries, as these 
organs cannot be formed in situ owing to the absence of 
interstitial cells in the tentacular ectoderm. At the same 
time I suggested that in those forms which do not possess 
tentacle-bulbs (Trachomedusae and Narcomedusae) these 
organs are replaced by the thickened ring of ectoderm con- 
taining stinging-cells, which is so conspicuous a feature of 
their anatomy. 
In order to investigate the structure of such a nettle-ring, 
sections, both radial and tangential, were cut through the 
umbrella edge of Limnocnida. 
These sections show that this organ has identically the 
same structure as the ocellar bulbs which I examined in 
Mcerisia lyonsi (5, p. 768). The nettle-ring consists of 
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