240 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



reached their maximum in October. In both regions, 

 also, Oikoyleura was present, though not in large 

 numbers, in July, but was absent in November. 



As regards Diatoms there is also fair similarity. 

 Rhizosolenia has already been noticed. In both localities 

 Asterionella, Biddulphia, Streptotheca and Thalassiosira 

 were absent in July, present in November. On the 

 other hand, Guinardia is absent from Station 14 in 

 November, but still present at Station 7 (the most 

 southerly). The various species of Chaetoceras also show 

 some resemblance. Their maximum seems to have 

 occurred at the southern Stations in October. A com- 

 parison of the three southern Stations with each other 

 does not appear to show much of interest. It is possible, 

 however, that a more extended series of observations will 

 give better grounds for comparison. One or two forms 

 may be noted. Thus Noctiluca only occurs twice, both 

 times at the most southerly of the three Stations. This 

 agrees with what has been previously observed in our 

 district, that Noctiluca is largely confined to the inshore 

 waters along the Lancashire and North Wales coasts. 

 Biddulphia sinensis, which now appears to be an estab- 

 lished form at Port Erin, is most common at Station 5, 

 where it occurs from November to January. It only 

 occurs at Stations 6 and 7 in December, and on this date 

 was most abundant at Station 5, much less common at 6, 

 and least at 7. This looks as if its occurrence was due 

 to a spreading from the south of the Isle of Man. On 

 the other hand, Rhizosolenia setigera is most common at 

 Station 7. It only occurs once at 5 and 6, and on this 

 date is much more abundant at 7. Thalassiothrix 

 nitzschioides never occurred at Station 5. On the other 

 hand, it was more common at 6 than at 7, 



