THE METEORS OF THE SEA. 15 



So vast are the numbers of these and other light-givers in 

 the northern seas, that the olive-green tints of the waters 

 are due to them in the daytime. Mr. Scoresby, finding 

 sixty-five of them in a cubic inch of water, summed up the 

 interesting calculation, that, if eighty thousand persons had 

 commenced at the beginning of the world (he refers to the 

 popular, not geological, reckoning,) to count, they would 

 barely at the present time have completed the enumeration 

 of individuals of a single species found in a cubical mile. 



One of the most remarkable of the Ctenophores is the 

 " Venus' girdle" QCestus veneris'), Plate V., Fig. 1. In shape 

 it differs from all others of the class, as a comparison between 

 it and the Beroe (Plate IV.), will show. It resembles in the 

 daytime a silvery ribbon, or girdle, two or three feet in 

 length, moving through the water by contractions of the 

 body, rather than by the rows of combs that are found upon 

 the edges. So delicate is this fragile creature, that it is almost 

 impossible to remove it intact from the water. The mouth 

 is in the centre, or equidistant between the ends ; and on 

 each side of it depends a short tentacle protruding from a 

 sac. Opposite the mouth there is an otocyst, or sense-body. 

 The combs, which are so conspicuous in other forms, are not 

 so noticeable here, yet are well defined ; and when moving 

 along, and propelled by these gentle undulations, the Cestus 

 is one of the most beautiful objects of the sea. At night this 

 wonderful sea-ribbon develops a new charm, emitting, accord- 

 ing to Giglioli, a reddish yellow light of singular brilliancy. 



The Ctenophores, from their phosphorescence and great 

 numbers, offer an interesting field for study. Pleurohrachia ^ 

 may be found in myriads upon our eastern shores in the 

 autumn. Idya i" attracts immediate attention by its won- 



