ON KEEPING MEDUSAE ALIVE IN AN AQUARIUM. 179 



The following notes on the inhabitants of the bell-jar may be of 

 interest: About eighty specimens of Obelia lived very well for about 

 ten days, and then began to die off. For the first week they kept in 

 splendid condition, and were very active, but were not seen catching 

 copepods. Obelia in an aquarium with still water usually lives about 

 twenty-four hours. 



Phialidium generally lives about three days in still water, but in the 

 " plunger " bell-jar one specimen (P. husJcianum) lived six weeks, 

 increased in size, and developed more tentacles. Its umbrella was as 

 transparent as the clearest glass, and its tentacles were often seen 

 stretched out, when fishing for copepods, to the fineness of a spider's web. 



Another old inhabitant of the bell-jar was Phialidium cymbaloideum. 

 In twenty-five days it added five new tentacles and five marginal bulbs. 



The medusa of Lar sahcllarum ( Willsia stdlata, Forbes) died suddenly 

 after five weeks' captivity. It also added new tentacles, and increased 

 the size of its umbrella. A specimen of Margdis lived seventeen days, 

 and during this period added two new tentacles in each of the four 

 marginal groups, and the oral tentacles twice dichotomously divided. 



A single specimen of Sarsia gcmmifcra was placed in on the 16th of 

 September. It started with six medusa-buds upon the manubrium ; 

 three of these developed into medusae which were liberated, and the 

 others had nearly completed their development by the 9th of October. 



These experiments I think show that it is possible to keep medusae 

 alive in confinement for several weeks without any change of water, 

 and that they increase in size and develop more tentacles. 



In this bell-jar I placed copepods and crustacean and worm larvae 

 as a food supply for the medusae. Whatever I placed in the bell-jar 

 I examined with a microscope, to see that the specimens were in 

 good condition. This applies not only to the medusae (it is useless 

 to place them in if at all damaged or about half dead), but also to 

 the copepods, &c. 



Fresh copepods were added when the stock became low ; some died 

 a natural death, and many others were captured by the medusae. I 

 did not try to keep alive the various pelagic larvae that were placed 

 in the bell-jar, but I noticed that they throve wonderfully well. The 

 larval form of Magelona was alive when I left Plymouth. It had 

 been several weeks in the bell-jar, and was often seen floating with 

 its two long tentacles stretched out to a considerable length. One 

 worm safely passed through its larval stages, and built a tube on 

 the bottom of the bell-jar. Mr. Gars tang identified the adult form 

 as Cajntella capitata. Several of the crustacean larvae passed through 

 their larval stages. I saw an adult form of a shrimp, and Mr. Hodgson 

 identified another crustacean for me as the adult of Nika edulis. 



