THE 



VOYAGE OF H.M.S. CHALLENGER. 



BOTANY. 



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

 Years 1873-76. By Conte Abate Francesco Castracane degli 

 Antelminelli. 



PREFACE. 



Although the group of the Diatomaceae was almost unknown until within the last half 

 century, the activity that has been exhibited in this very attractive department of 

 research has of recent years been so great that many hundreds of different species have 

 been already recorded. Two branches of the study, however, possess perhaps a more than 

 ordinary amount of interest. Among the numerous types that occur in the more super- 

 ficial waters of the ocean, or that have sunk to the bottom and now form part of the 

 oozes of the ocean bed, many unusual forms which are the representatives of several of 

 the most elegant of known genera have been met with, while many geological deposits of 

 marine or lacustrine origin, and occurring in various parts of Italy and in Sicily, as well 

 as several other regions of the globe, not unfrequently present rare and superb frustules. 



Having for several years occupied myself with the careful study of many marine 

 soundings and with the examination of various geological deposits, and having taken 

 pains to procure frustules from various parts of the world for comparison with those 

 found in such deposits by communicating with other well-known micrographers, I lost no 

 time on the return of H.M.S. Challenger in expressing to the naturalists at the head of 

 the Commission the desire that I might procure from them spare materials for the 

 purpose of facilitating my work. The courteous assurance that this request would in due 

 time be attended to afforded me great satisfaction, and this was still further increased 

 when, after writing to Dr Radford of the importance of instituting a comparison between 

 the Italian deposits and the Antarctic diatomaceous banks first made known by Sir J. D. 



(bot. CHALL. EXP. — PART IV. — 1886.) a 



