SEA-FISHERIES LABORATORY. 237 



Dinoflagellates, and Rhizosolenia. On November 7th 

 there is a decrease in the numbers of Copepoda, and 

 a marked decrease in the Dinoflagellates, while 

 RJn'zosolenia has disappeared and been replaced by other 

 Diatoms. We may note here that a surface haul in 

 Luce Bay on October 22nd showed Rhizosolenia still 

 present in the inshore waters in fair numbers, but other 

 forms, Biddulphia, Chaetoceras, Ditylium and Thalas- 

 siosira, had also made their appearance. This succession 

 of forms in autumn corresponds to what has been observed 

 at Port Erin. 



If we contrast these two hauls with those taken at 

 the more southerly Stations (5, 6, 7) on corresponding 

 dates, we shall see that while there are some points of 

 resemblance there are also some marked distinctions. 

 As regards Copepoda the result is much the same, the 

 drop in numbers being, however, more marked at the 

 southern Stations. At both localities Pseudocalanus is the 

 most common Copepod in November, while Temora has 

 disappeared. Sagitta also shows a correspondence. 

 Rhizosolenia, however, is different, being still present at 

 the southern stations in November. 



But the most marked difference is in the Dino- 

 flagellates; here the two localities show directly opposite 

 conditions. At the southern Stations Dinoflagellates, 

 except Peridiniuin, were absent at the end of July, while 

 in November they appear to be at their maximum. They 

 are still present in March. 



The Tintinnidae also show some resemblance. At 

 Station 14 these were absent in July, and present in fairly 

 large numbers in November. At the southern Stations 

 they were present in July at Station 5 only, and in 

 comparatively small numbers. In November they are 

 present in large numbers, though they appear to have 



