220 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



18th, Station III, 20-10 = 0'9 c.c, 20-0 = 15 c.c. ; but in 

 other cases again we find that the two hauls are roughly 

 equal in volume, indicating that the bulk of the plankton 

 is in the zone below 10 fathoms from the surface, as for 

 example, April 11th, Stat. I., 20-10 and 20-0 fathoms, 

 both = 0*6 c.c. The medium Nansen (50 cm. diameter) 

 hauled on the same occasion from 20-0 fathoms gave 

 16 c.c; and from this to three times seems the usual 

 proportion between these two nets when hauled vertically 

 together. 



The medium Hansen, and also the large Nansen 

 (100 cm. diam.) were sometimes towed horizontally, like 

 the shear-net, when it was desired to obtain not a standard 

 haul for statistical comparison, but a large bulk of 

 material for some special purpose. 



In comparing the hauls, taken with exactly similar 

 nets, in the bay on the one hand and in the open sea 

 from the yacht on the other, we find that both in spring 

 and in autumn the hauls from the sea outside were on 

 the whole larger than those from the bay. The difference 

 is usually not very large, but the records seem to indicate 

 that the amount of plankton (Diatoms, Dinoflagellates 

 and Copepoda) in the open sea is rather greater than that 

 in the bay during April, August and September. 



WEATHER CONDITIONS. 



The weather during 1911 was certainly exceptional, 

 and this might be expected possibly to have some effect 

 upon the amount of the plankton. The spring was cold, 

 and the latter part of the summer (especially August) was 

 unusually dry and warm. Professor Bassett, in his 

 article on the Hydrography of the Irish Sea in 1911, 

 associates these weather conditions with an unusually 



