344 OBSERVATIONS OS LUMINOUS ANIMAL* 



assign, as it is varied by partial contractions, at the ani- 

 mal's pleasure. I hare represented the two extremes of 

 form, that I hare 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 pro. 

 per shape: the other resembles a pear, and is the figure it 

 has in the most contracted state. The body is hollow, ox 

 forms internally an infundibular cavity, which has a wide 

 opening before, and appears also to haye 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 luminous beroe, 

 which I suspect was no other than the species I am now 

 giving an account of. 

 Light emitted When the beroe fulgens swam gently near the surface of 

 ^y"- 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 com- 

 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 a light like 

 that of phosphorus ; this however, as well as every other 

 mode of emitting light, ceased after the death of the 

 animal. 

 Keipisphcrical The hemispherical species of medusa, that I discovered, 

 jjnedusa. jj^^j ^ y^^y f^jnt purple colour. The largest that I found, 



measured about three quarters of an inch in diameter. The 

 Jnargin of the umbelia was undivided, and surrounded ini 

 ternally by a row of pale brown spots, and nuraerons 

 small twisted tentacula: four opaque lines crossed in an 

 arched manner from the circumference towards the centre 

 of the animal: an opaque irregular shaped process hung 

 down from the middle of the umbeila; when this part was 

 examined with a lens of high powers, I discovered that it 

 ^^ was inclosed in a sheath in whidi it mov^d, and that the 



c>.trc'anty 



