382 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



interpretation of the facts, then our record shows that 

 the species had extended to the centre of the Irish Sea 

 in 1909, and that here, as elsewhere, it reached a 

 maximum in November. It is, however, possible that 

 we have in all these records the unusual increase of a 

 rare species which had previously escaped observation." 

 The specimens of Biddulphia sinensis noticed during 

 the first year of its occurrence in our' area were single 

 cells, as shown in figs. 1 and 2 on PI. I. There was 

 not the slightest indication of increase in numbers by cell 

 division. 



On p. 207 of the XlXth Annual Eeport (1910) 

 we state: "The Indo-Pacific Diatom, Biddulphia 

 "sinensis, which has appeared recently in our N.W. 

 " European seas, is again present at Port Erin in 

 " November in quantity. 



" It seems now, from its appearance in the gather- 

 " ings, to be in much more vigorous condition than when 

 " it first occurred in the Irish Sea. The cells are seen 

 "to be in active division, and chains of two and four 

 " cells adhering together are quite frequently seen." 



The general appearance of the dividing Biddulphia 

 sinensis in 1910 is shown by fig. 3 on the Plate. It agrees 

 fairly well with the text-figure given by Ostenfeld on 

 p. 363 of the " Internationale Pevue d. Hydrobiologie 

 und Hydrographie," Bd. II, 1909. Up to this time 

 all appeared to be well with Biddulphia sinensis in our 

 district, and it was acting just as a sound species ought. 

 It again made its appearance in the autumn of 1911, and 

 for a time continued in a normal condition. Towards 

 the end of that year, however, odd specimens were 

 noticed which showed a departure from the true sinensis 

 form, and appeared to be adopting some of the characters 

 of Biddulphia mobiliensis. We state on p. 138 of the 



