COLLECTING DIATOMS. 39 



of this light flocculent surface mud. This will be almost sure to 3 ield 

 some fine diatoms, such as Campylodiscus spiralis, Pinnularia nobilis 

 Stanroneis Phcenicenteron, Surirella splendida, and Cymatopleura solea. 



" Here we must finish our day's work, having arrived at the railway 

 station, from whence we proceed home with our treasures. The work 

 of collecting has been finished, yet much remains to be done before the 

 material is cleansed and mounted on slides for microscopical investigation. 



" Let us hope our fatigue has not been in vain, but that the store 

 of riches we have collected together will furnish us with ample material 

 for much interesting study and instruction." 



B. Marine and Pelagic Collections. 



To obtain an exhaustive knowledge of diatoms, it will not be 

 sufficient to study those forms only which are met with in streams, on 

 the banks of rivers, and on the sea shore, for in that case our knowledge 

 of them would be very incomplete indeed ; but we must also examine all 

 fossil deposits as well as marine and pelagic diatoms. 



It is in fact, just as important to obtain forms which are found at the 

 bottom of the sea as those which float just under water or on the surface 

 of the ocean and the mouths of large rivers. It is only of late years that 

 it has been discovered how numerous are these floating forms to which 

 the name Pelagic diatoms ( x ) has been given, and how much they vary 

 according to the seasons and under the influence of currents and other 

 causes which have not yet been completely ascertained. 



For the last eight years I have specially devoted myself to the study 

 of marine and pelagic forms, and have made hundreds of gatherings of 

 them, and for this purpose I have used my steam yachts " Nautilus " 

 and " Suzon." The former is specially constructed for exploring the upper 

 Scheldt ; it is a flat-bottomed paddle-boat, and by reason of its small 

 draught and the special form of its keel it can navigate shallow water 

 with impunity. I have used this yacht most frequently in making gatherings 

 in the upper Scheldt between Ghent and Saftingen, while the "Suzon" ( 2 ) 

 has been used for the lower part of the river and the North Sea. 



( ) It would be better to describe these diatoms as Floating, or Wandering. The Germans 

 use the word " Plankton " (from -rrXayKrog wandering, roaming) to denote all living organisms 

 which are displaced in this way under the influence of currents, &c. 



(") The "Suzon" comes from the shipyard of Messrs. Watkins and Co., of London, who 

 are considered among the most skilful yacht-builders in England. The " Suzon " is con- 

 structed entirely of teak wood, having a draught of 6ft. Its length is 60ft. , and breadth njft. 

 Being very narrow and fitted with powerful machinery it can, when running with the tide, 

 make nearly n knots, and can carry coal to last eight days. 



