190T. Delap. — Rearing oj Chrysaora isosceles. 27 



in diameter. On June 21st the umbrella had increased to 6£ 

 inches in diameter and 3 inches in thickness ; the frilled 

 oral arms extended to the bottom of the bell-jar. The colouring 

 of the marginal lobes and the top of the umbrella was now 

 as bright as in a specimen taken from the sea — a rich dark 

 brown colour. 



About July 8th the medusa— 13 weeks old — reached its 

 maximum growth. The umbrella was 9 inches in diameter ; 

 the oral arms and tentacles extended to the bottom of the 

 bell-jar. The gonads were visible, showing quite yellow 

 through the umbrella. 



The difficulty of obtaining a sufficient food supply owing to 

 the stormy state of the weather, and the increased tempera- 

 ture of the water, gradually affected the.health of the medusa. 

 It began slowly to decrease in size, the umbrella became 

 smaller in diameter, and the oral arms and tentacles shorter. 

 It spent, too, a great deal of its time at the bottom of the bell- 

 jar bumping the top of the umbrella upon the gravel, instead 

 of swimming round and round at the surface. By August 13th 

 its condition became critical, and as it was not likely to live 

 much longer I preserved it in a solution of formaline. The 

 umbrella had decreased to 6 inches in diameter. 



The chief trouble connected with the rearing of this medusa 

 was to obtain a sufficient supply of food ; its appetite was 

 enormous. I soon found out what kind of food Chrysaora 

 preferred by placing different pelagic animals in the bell-jar, 

 and watching the result. 



It had a great liking for small Antho-medusae and L,epto- 

 medusae, such as Corymorpha, Margelis, Sarsia, Ampkinema, 

 Phialidium, Laodice, Euchilota, &c. ; also for the siphonophore 

 Agalmopsis, and the ctenophores Pleurobrachia and Bolina. 

 It had no objection to Tomopteris and 1 Sagitta. There were, 

 however, two animals it would not touch, even after a few days' 

 starvation — the antho-medusa Tiara pileata, and the cteno- 

 phore Beroe ovata. It is well known that young fish are often 

 found under the umbrella of the large Scypho- medusae, 

 especially Pilema {Rhizostomd) octopus. One day I put a small 

 fish, about an inch in length, into the bell-jar. The medusa 

 caught it and held it for some time in the frills of the oral 

 arms, but finally let it go without doing any harm to it. I 

 kept afterwards two small fish for some weeks in the bell- 



A*2 



