180 ON KEEPING MEDUSAE ALIVE IN AN AQUARIUM. 



Ill another plunger bell -jar I placed a colony of Syncoryne. It 

 soon sent out long stolons attached to the glass. I measured and 

 made drawings, at intervals, of the new growth of the colony. In 

 thirteen days the total length of the new stolons and branches 

 amounted to 773 mm., and ninety-nine new hydianths appeared. In 

 this bell-jar I also kept some medusae liberated from hydroid colonies 

 of Pcrigonimus. When the medusa leaves the colony it has two long 

 perradial tentacles. In twelve days one specimen possessed four long 

 perradial tentacles, four interradial bulbs, and one adradial bulb. 

 The other specimens were not quite so far advanced. 



I tried the experiment of starting with a perfectly clean bell-jar and 

 using filtered sea-water, in which a plunger worked. Into this bell- 

 jar, holding about two gallons, I placed about three dozen medusae 

 and a good supply of copepods. The medusae were not specially 

 selected, but taken as a sample of a day's tow -netting. I did not 

 interfere with them for ten days, but only added copepods when the 

 supply became low, when I found thirty -one specimens alive, and 

 more than half of them were in excellent condition. 



I must express my sincere thanks to my friend Mr. E. J. Allen 

 for the great amount of trouble and the many useful suggestions 

 which he made when we fitted up the apparatus for working the 

 first plunger bell -jar. It was his suggestions which led to the 

 plunger being worked by such a simple method. 



