Observations upon Luminous Animals. 99 
tlaally they were so transparent as. to be perfectly invisi- 
ble, except under particular circumstances. Their substance 
was indeed so extremely tender and delicate, that they did 
not hecome opake in distilled vinegar or alcohol, until im- 
mersed in these liquors for a considerable time, 
On examining these minute globules with the microscope, 
T found that they were not quite perfect spheres, but had 
an irregular depression on one side, which was formed of 
au opake substance, that projected a little way inwards, pro- 
ducing such an appearance as would arise from tying the 
neck of a round bag, and turning it into the body. 
The motions of these creatures in the water were slow 
and graceful, and not accompanied by any visible contrac- 
tion of their bodies. Atier death they always subsided te 
the bottom of the vessel. 
From the sparkling light afforded by this species, E shall 
distinguish it by the name of medusa scintillans. 
The night following that on which I discovered the pre- 
eeding animal, I caught the two other luminous species. 
One of these I shall call the beroe fulgens. 
This most elegant creature is of a colour changing be- 
tween purple, violet, and pale blue: the body is truncated 
before, and pointed behind; but the form is difficult to as- 
sign, as it is varied by partial contractions, at the animal’s 
pleasure. 1 have represented the two extremes of farm 
that I have seen this creature assume: the first is some- 
what that of a cucumber, which, as being the one it takes 
when at rest, should perhaps be considered as its propee 
shape: the other resembles a pear, and is the figure it has. 
in the most contracted state. The body is hollow, or forms 
internally an infundibular cavity, which has a wide opening 
before, and appears also. to havea small aperture posteriorly, 
through which it discharges its excrement. The posterior 
two-thirds of the body are ornamented with eight longitudi- 
nal ciliated ribs, the processes of which are keptin such a. 
rapid rotatory motion, while the animal is swimming, that 
they appear like the continual passage of .a fluid along the 
nibs. . The ciliated ribs have been described by Professor 
Mitchell, as arteries, in a luminous beroe, which I suspect 
wus no other than the species ] am now giving an ac- 
sount of, 
When the beroe fulgens swam gently near the surface of 
the water, its. whole body became occasionally illuminated 
in a slight degree; during its cantractions, a stronger light 
ipsued trom the ribs; and when a suddea shock was com- 
municated 
