THE 



VOYAGE OF H.M.S. CHALLENGES. 



ZOOLOGY. 



REPORT on the Siphonophor^e collected by H.M.S. Challenger during 

 the Years 1873-76. By Ernst Haeckel, M.D., Ph.D., Hon. F.R.S.E., 

 Professor of Zoology in the University of Jena. 



PEEFACE. 



The Siphonophorse collected by the Challenger during her cruise round the world 

 were handed to me for investigation in 1879. The examination of this material, 

 among which were to be found many new and remarkable types (especially abyssal 

 forms), led me to recommence my study of the organisation and development of 

 the whole class, which had been interrupted for more than ten years. During a 

 residence of three months at Puerto del Arrecife, the harbour of Lanzerote in the 

 Canary Islands, December 1866, January and February 1867, I had the opportunity 

 of becoming acquainted with nearly all the typical forms of this most attractive group 

 of animals. The facts which I then discovered regarding the curious, but till then 

 little known, ontogenesis of these Acalephs, were embodied in a prize essay published 

 by the Gesellschaft fiir Kunst und Wissenschaft in Utrecht. 1 I then intended to 

 follow up this embryological memoir with a more extensive comparative anatomical 

 one, or if possible a Monograph, in which also the systematic arrangement of the 

 Siphonophoras should be subjected to a thorough revision, and the very intricate 

 literature of this class critically elucidated. The completion of this scheme was, 

 however, deferred owing to various external hindrances, and the rich material collected 

 at Lanzerote remained for the most part unpublished. 



1 Zur Entwickelungsgeschichte der Siplionophoren, Utrecht, 1869, 14 plates. 

 (ZOOL. CHALL. EXP. — PART LXXVII. — 1888.) Hhbh a 



