iv THE VOYAGE OF H.M.S. CHALLENGER. 



drawn from spirit specimens, to take advantage of my knowledge of the forms of the 

 living Medusae, to reconstruct the most probable approximate image of the living forms. 

 I was greatly assisted in my efforts in this direction by the skilful hand of my litho- 

 grapher, Mr. Adolf Giltsch. I am also greatly indebted to my friend Dr Keinhold 

 Teuscher for preparing a large number of excellent microscopic sections. This Memoir 

 has been translated into English by Miss Nellie Maclagan, and I thank her for the kind 

 care with which she has executed a difficult task. 



The many new morphological facts, furnished by close examination of the deep-sea 

 Medusae, are not only of special interest in themselves, but are, for the most part, of 

 general interest for deciphering the comparative anatomy of the whole class ; this is true, 

 for example, of the Pectyllidse and Peganthidae among the Craspedotae, and of the 

 Periphyllida? and Ephyridae, among the Acraspedae. I therefore considered it convenient 

 to preface the special anatomical description of the eighteen deep-sea Medusae by a short 

 article on the Organisation of the Medusae, which serves in a certain measure as a mor- 

 phological introduction to the former, and at the same time as a preliminary Scheme 

 of a comparative Morphology of the Medusae. 



EENST H^ECKEL. 

 Jena, lith September 1881. 



