2 66 
Mr. Macartney's Observations 
and pointed behind ; but the form is difficult to assign, as it 
is varied by partial contractions, at the animal's pleasure. I 
have represented the two extremes of form that I have seen 
this creature assume : the first is somewhat that of a cucumber, 
which as being the one it takes when at rest, should perhaps 
be considered as its proper 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 
have a small aperture, posteriorly through which it discharges 
its excrement. The posterior two-thirds of the body are 
ornamented with eight longitudinal ciliated ribs, the processes 
of which are kept in such a rapid rotatory motion, while the 
animal is swimming, that they appear like the continual 
passage of a fluid along the ribs. The ciliated ribs have 
been described by Professor Mitchell, as arteries, in a lumi- 
nous beroe, which I suspect was no other than the species I 
am now giving an account 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 contractions, a stronger light 
issued from the ribs, and when a sudden shock was commu- 
nicated to the water, in which several of these animals v ere 
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 a light 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 
