CHAPTER XIV 



PLANKTON {continued) : ITS VARIATIONS AND ITS 



PROBLEMS 



There are many other problems of the plankton in addition 

 to those of the quantitative estimates — possibly even some 

 that we have not yet recognized— and various interesting 

 conclusions may be drawn from some recent planktonic 

 observations. Here is a case of the introduction and rapid 

 spread of a form new to British seas. 



Biddulphia sinensis (see Fig. 1 on Plate XXII) is an exotic 

 Diatom which, according to Ostenfeld, made its appearance 

 at the mouth of the Elbe in 1903, and spread during succes- 

 sive years in several directions. It appeared suddenly in 

 our plankton gatherings at Port Erin in November, 1909, 

 and has been present in abundance each year since. 

 Ostenfeld, in 1908, when tracing its spread in the North Sea, 

 found that the migration to the north along the coast of 

 Denmark to Norway corresponded with the rate of flow of 

 the Jutland current to the Skagerak — viz. about 17 cm. 

 per second— a case of plankton distribution throwing light 

 on hydrography — and he predicted that it would soon be 

 found in the English Channel. Dr. Marie Lebour, who 

 recently examined the store of plankton gatherings at the 

 Plymouth Laboratory, finds that as a matter of fact this 

 form did appear in abundance in the collections of October, 

 1909, within a month of the time when according to our 

 records it reached Port Erin. Whether or not this is an 

 Indo -Pacific species brought accidentally by a ship from the 

 Far East, or whether it is possibly a new mutation which 



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