170 HAECKEL 



became known, in the thirties or forties, the 

 medusae were regarded as amongst the most 

 interesting objects in the whole of zoology. They 

 offered an extremely difficult task to the investi- 

 gator who would care to take up the study of 

 them. 



When Haeckel was with Johannes Miiller in 

 Heligoland in 1854 he made acquaintance with 

 them for the first time. His artistic eye was 

 caught with their beauty, as it was afterwards 

 with the radiolaria. " Never shall I forget," he 

 says, ^* the delight with which, as a student of 

 twenty years I gazed on the first Tiara and Irene 

 [species of medusae] , and the first Chrysaora and 

 Cyanea, and endeavoured to reproduce their 

 beautiful forms and colours." His predilection 

 for the medusae never disappeared. At Nice 

 in 1856 he met them again in the Mediterranean. 

 Gregenbaur's Sketch of a Classification of the Me- 

 duscR provided his studies with a starting-point, 

 just as Miiller 's writings did afterwards for the 

 radiolaria. At Naples and Messina he completed 

 his mastery of them. When he had done with 

 the radiolaria for the time after publishing the great 

 monograph of 1862, the next task that loomed up 

 on his horizon was the need for a " monograph on 

 the medusae." It would be a long time, however, 

 before he could complete the work in any fulness. 

 A work of Agassiz that purported to do it, but, in 

 his opinion, only confused the subject — he disliked 

 both the Agassizs, father and son, and the father 

 became one of his bitterest opponents on the 



