COLLECTING DIATOMS. 4 1 



at all events, only make the slightest headway. Any attempt to go quicker 

 is useless, for it will be quite impossible to obtain gatherings, owing to 

 the fact that there would not be time for the water to filter through the 

 net, and there is also a risk of tearing or even of altogether losing the 

 net by the cords getting broken. 



From time to time the nets are drawn in on to the deck of the 

 vessel, and are carefully washed in a pail of water, which is left standing 

 for a considerable time. After decanting the supernatant liquid, the 

 sediment in the bucket is put into bottles, which are then carefully labelled, 

 to avoid any subsequent confusion. 



From pelagic gatherings many very rare forms may often be obtained 

 in great abundance which are only met with exceptionally in shore mud. 

 The following is a list of diatoms found in a pelagic gathering made at 

 Hansweert, a maritime partion of the Scheldt, about 31 miles from 

 Antwerp, on the 22nd May, 1892 : 



Rhizosolenia setigera. 

 Shrubsolii. 



Plagiogramma Van Heurckii. 



Synedra nitzschioides. 



Eucampia Zodiacus. 



Chsetoceros Wighamii. 



Ditylum Brightwellii. 



Biddulphia Isevis. 



Coscinodiscus Oculus Iridis. 

 concinnus. 



Lithodesmium undulatum. 



Actinoptychus (Secondary valve = Debya insignis). 



Triceratium Favus. 



Campylosira cymbelliformis. 



Skeletonema (Melosira) costatum (Grev.), Grun. 

 Up to the present time we have only incomplete data as to the origin, 

 the rapidity of propagation, and the direction which these masses of float- 

 ing diatoms take on our coasts. It will depend upon the littoral currents, 

 of which we have no information, and on the sea currents which give 

 rise to the "flow"('), a current which sets out from the English Channel 

 coast along the Belgian shore, bearing E.N.E. to N.E., and the ebb tide 

 (reflux or descending sea), which comes down from N.N.E., and takes a 



( r ) Etude sur les courants de la Mer du Nord par. M. Petit, Directeur du service de 

 1 hydrographie de Belgique. Anvers. Tessaro. 1892. 



