30 Observations upon Luminous Animals. 
municated to the water, in which several of these animals 
were placed, a vivid flash was thrown out. If the body 
were broken, the fragments continued luminous’ for some 
seconds, and, being rubbed’on the hand, left alight like that 
of phosphorus: this however, as well as every other mode 
of emitting light, ceased after the death of the animal. 
The hemispherical species that-I discovered, had a very 
faint purple colour. The largest that I found, measured 
about three quarters of an inch in diameter. The margin 
of the umbella was undivided, and surrounded internally 
by a row of pale brown spots, and numerous small twisted 
tentacula: four opake lines crossed in an arched manner 
from the circumference, towards the centre of the animal: 
an opake irregular shaped process hung down from the. 
middle of the umbella: when this part was examined with 
alens of high powers, I discovered that it was inclosed in. 
a sheath in which it moved, and that the extremity of the 
process was divided into four tentacula, covered with little 
cups or suckers, like those on the tentacula of the cuttle-fish. 
This species of medusa bears a striking resemblance to 
the figures of the medusa hemispherica, published by Gro- 
novius and Muller; indeed it differs as little from these 
figures, as they do'from each other. Its luminous property, 
however, was not observed by these naturalists; which 1s 
the more extraordinary, as Muller examined it at night, and 
says it is so transparent that it can only be seen with the 
lightofalamp. If it should be still considered as a distinct 
species, or as a variety of the hemispherica, I would pro- 
pose to call it'the medusa lucida. 
In this species, the central part and the spot round the 
margin are commonly seen to shine on lifting the animal 
out of the water into the air, presenting the appearance of 
an illuminated wheel; and when it is exposed to the usual 
percussion of the water, the transparent parts of its body 
are alone luminous. 
In the month of September 1805, 'T again visited Herne 
Bay, and frequently had opportunities of witnessing( the 
luminous appearance of the sea. ‘I caught many of the 
hemispherica! and minute species of! medusa, but not one 
of the beroe fulgens. I observed that these luminous ani- 
mals always retreated from the surface of the water, as soor 
as the moon rose. I found also, that exposure to the day- 
light took away their property of shining, which was re- 
aived by placing them for some time in a dark situation. 
Fn that season Ishad two opportunities of seeing an ex- 
tended 
