PLANKTONIC STUDIES. 573 



II.— PLANKTONIC STUDIES. 



My own investigatious on the organisms of the plankton were begun 

 thirty-six years ago, when I got my lirst conception of the wonderful 

 richness of the marine fauna and iiora in the North Sea. Accepting 

 the kind invitation of my ever-remembered teacher, Johannes Miiller, 

 I accompanied him in the autumn of 1854 on a vacation trip to Helgo- 

 land, and was introduced by him personally into the methods of plank- 

 ton fishery and the investigation of the pelagic fauna. There, during 

 August and September, I accompanied him daily on his boating trips, 

 and under all conditions of the rich planktonic captures I received from 

 him the most competent instruction, and pressed with corresponding 

 eagerness into the mysteries of this wonderful world. Never will I for- 

 get the astonishment with which I first beheld the swarms of pelagic 

 animals which Miiller emptied by inversion of his "fine net" into a glass 

 jar of sea water— a confused mass of elegant medusae and glistening 

 ctenophores, swift-darting sagittas and snake-like tomopteris, copepods 

 and schizopods, the pelagic larvre of worms and echinoderms. The 

 important stimulus and instruction of the founder of planktonic inves- 

 tigatio^n has exercised a constant infiuence on my entire later life, and 

 has given me a lasting interest in this branch of biology.* 



Two years later (in August and September, 185G), while at Wiirtz- 

 burg, I accepted the invitation of my honored teacher, A. Kolliker, to 

 accompany him to Mzza, and, under his excellent guidance, became 

 acquainted with the zoological treasures of the Mediterranean. In 

 ct)mpauy with Heinrich Miiller and K. Knpfifer, Ave investigated espe- 

 cially the rich pelagic aninnil life of the beautiful bay of Villafranca. 

 Tliere, for the first time, I met those wonderful forms of the pelagic 

 fauna which beh)ng to the classes of the siphonophores, pteropods, and 

 heteropods. I also there first saw living polycyttaria, acanthometra, 

 and polycystina, those phantasmic forms of radiolaria, in the study of 

 which I spent so many later years. 



Johannes Miiller, who was at this time at Nizza, and had already 

 begun his special investigation of this latter order, called my attention 

 to the many and important questions which the natural history of 

 these enigmatical microscopical organisms present. These valuable 

 suggestions resulted some years later in my going to Italy and spend- 

 ing an entire year in pelagic fishing on the Mediterranean coast. Dur- 



* When at Helgoland, investigating the wonders of the plankton with the micro- 

 scope, Johannes Miiller, pleased with the care and patience Avith which his zealous 

 students tried to study the charming forms of meduste and ctenophores, spoke to me 

 the ever-memorable words, "Tliere you can do much; and as soon as you have 

 entered into this pelagic wonderland you will see that you can not leave it." 



