LIMNOCNIDA TANGANICJE. 
89 
migrating towards the more distal regions, and they form a 
regular stream moving towards the nematocvst batteries 
further along the tentacles. In the region of the first few 
rings of batteries the stinging-cells can be seen grouping 
themselves together to form these characteristic organs (Text- 
fig. 1, x). 
The next point to consider is the origin of these wandering 
cells, and one’s attention is naturally drawn to the nettle- 
ring ; examination of longitudinal sections through the points 
where the tentacles are given off from the umbrella- edge 
shows that the stinging-cells are actually proceeding from this 
thickened ring of ectoderm (PI. 15, fig. 2). 
From the above considerations it is safe to argue that the 
nettle-ring of Limnocnida is not a defensive organ, but has 
to be considered as the factory and storage-place of the ten- 
tacular stinging-cells. 
3. The Nervous System. 
Gunther was unable to find any trace of a nervous system in 
Limnocnida, although he made special search for a nerve- 
ring in the neighbourhood of the base of the velum. This 
was probably due to the state of preservation of his specimens. 
Radial sections of my own showed the nerve-ring in its usual 
position. It has much the same structure as in other Cras- 
pedote medusae. 
The ring of nerve-fibres is situated on the edge of the 
nettle-ring at the base of the velutn and is double, the two 
parts being separated by the structureless lamella of that 
organ (PI. 15, fig. 3). As in Limnocodium (Gunther [7]), 
the outer nerve-ring is much better developed than the inner 
ring, aud in transverse sections is seen to be surrounded by a 
number of small cells which form a kind of sheath. The 
sense-organs are in close proximity to the outer nerve-ring, 
but I was unable to trace any definite nerve-endings in these 
organs. This was probably due to the very poor staining 
properties of the nerve-fibres. The inner ring of fibres is 
