L 17G J 



On Keeping Medusae Alive in an Aquarium. 



By 



Edward T. Browne, 

 University College, London. 



I HATE made several attempts to keep medusae alive in an aquarium, 

 but have only recently been successful. A medusa when first placed 

 in an aquarium swims actively about, but in a few hours it sinks to the 

 bottom apparently tired out. After an interval of rest it takes another 

 swim and again sinks to the bottom. This is repeated until the medusa 

 becomes completely exhausted ; then it stays at the bottom and slowly 

 dies. In spite of every attention, plenty of clean sea-water, plenty of 

 copepods, and a suitable temperature, I found that my medusae often 

 used to die within a day of their capture. 



When I have been watching medusae at the surface of the sea, I 

 have noticed that they simply float along with the tide without 

 often pulsating the umbrella. In my bell-jars the water was perfectly 

 motionless, so that a medusa had to pulsate its umbrella in order to 

 keep afloat, and as soon as the pulsations stopped it began to sink. 

 There are some species, like those belonging to the Bougainvillidae, 

 which live longer in confinement, as they are able to poise themselves 

 in the water by the extension of their tentacles and remain motionless 

 for long periods, but even these finally reach the bottom of the bell-jar, 

 and a long period at the bottom ends in death. 



It appeared to me that to keep medusae alive in an aquarium it was 

 necessary to have the water in motion so that a medusa could float 

 about just as it does in the sea, without having constantly to pulsate 

 its umbrella. The intervals of floating are periods of rest. 



I pass over the early experiments and describe a simple method for 

 keeping water in motion in a bell-jar, which has given excellent results 

 and has enabled me to keep medusae alive for many weeks in perfect 

 condition. The current in the water is obtained by simply moving up 

 and down, fairly slowly, a glass plate inside a bell-jar. Owing to the 



