NATURAL HISTORY. 



635 



tender and delicate, that they did 

 not become opake in distilled vine- 

 gar or alcohol, until immersed in 

 these liquors for a considerable 

 time. 



On examining theseminute glo- 

 bules with the microscope, 1 found 

 that the}' were not quite perfect 

 spheres, but had an irregular de- 

 pression on one side, which was 

 formed of an opake substance, 

 that projected a little way inwards, 

 producing such an appearance as 

 would arise from tying the neck 

 of a round bag, and turning it into 

 the body. 



I ' The motions of these creatures 

 in the water were slow and grace- 

 ful, and not accompanied by any 



^ visible contraction of their bodies. 



" After death they always subsided 

 to the bottom of the vessel. 



From the sparkling light afford- 

 ed by this species, I shall distin- 

 guish it by the name of medusa 

 scintillans. 



The night following that on 

 which I discovered the preceding 

 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 between purple, 

 violet, and pale blue : the body is 

 truncated before, and pointed be- 

 hind ; but the form is difficult to 

 assign, as it is varied by partial 

 contractions, at the animal's plea- 

 sure. 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 con- 

 tracted state. The body is hol- 



low, or forms internally an infun- 

 dibular cavity, which has a wide 

 opening before, and appears also 

 to have a small aperture posterior- 

 ly, through which it discharges its 

 excrements. 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 mo- 

 tion, while the animal is swimming, 

 that they appear like the con- 

 tinual 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. 



When the beroe fulgens swam 

 gently near the surface of the 

 water, its whole body became oc- 

 casionally illuminated in a slight 

 degree; during its contractions, a 

 stronger light issued from the ribs: 

 and when a sudden shock was 

 communicated 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 2 

 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 three quar- 

 ters of an inch in diameter. The 

 margin of the umbella was undi- 

 vided, and surrounded internally 

 by a row of pale brown spots, and 

 numerous small twisted tentacular 

 four opake lines, crossed in an 



