MARINE ANIMALS — MEDUSA. 25 



scarcely seen any other animals than terns (or sea- 

 swallows) and a few dolphins ; but on the 11th June 

 they entered a zone in which the whole sea was 

 covered with a prodigious quantity of medusae. The 

 vessel was almost becalmed ; but the molusca ad- 

 vanced towards the south-east with a rapidity equal 

 to four times that of the current, and continued to 

 pass nearly three-quarters of an hour, after which 

 only a few scattered individuals were seen. Among 

 these animals they recognised the Medusa aurita of 

 Baster, the M. pelagica of Bosc, and a third approach- 

 ing in its characters to the M. hysocella, which is dis- 

 tinguished by its yellowish-brown colour, and by 

 having its tentacula longer than the body. Several 

 of them were four inches in diameter, and the bright 

 reflection from their bodies contrasted pleasantly 

 with the azure tint of the sea. 



On the morning of the 13th June, in lat. 34"^ 33', 

 they observed large quantities of the Dagysa nolala, 

 of which several had been seen among the medus£e, 

 and which consist of little transparent gelatinous 

 sacs, extending to 14 lines, with a diameter of 2 or 

 3, and open at both ends. These cylinders are lon- 

 gitudinally agglutinated like the cells of a. honey- 

 comb, and form strings from six to eight inches in 

 length. They observed, after it became dark, that 

 none of the three species of medusa which they had 

 collected emitted light unless they were slightly 

 shaken. When a very irritable individual is placed 

 on a tin plate, and the latter is struck with a piece of 

 metal, the vibrations of the tin are sufficient to make 

 the animal shine. Sometimes, on galvanizing me- 

 dusae, the phosphorescence appears at the moment 

 when the chain closes, although the exciters are not 

 in direct contact with the body of the subject. The 

 fingers, after touching it, remain luminous for two 

 or three minutes. Wood, on being rubbed with a 

 medusa, becomes luminous, and after the phospho- 

 rescence has ceased, it may be rekindled by passing 



