70 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



have been even more restricted. Under these circum- 

 stances, an observation made solely in the water traversed 

 during the first seven minutes would have given a very 

 different result from that actually obtained; or, to put it 

 another way, had two expeditions taken samples that 

 evening at what might well be considered as the same 

 station, but a few hundred yards apart, they might have 

 arrived at very different conclusions as to the constitution 

 of the plankton in that part of the ocean. 



We have a good deal of evidence as to the distribution 

 of the organisms in horizontal zones ; and, when Diatoms 

 are not present in great quantity, the most prolific zone 

 off Port Erin seems to be from 5 to 10 fathoms below the 

 surface. 



As an example of a case where two similar nets 

 hauled side by side gave very nearly the same amount of 

 material, but w T here the kinds and numbers of organisms 

 present in the catch when examined were found to be 

 very different, I give the following lists of the contents* 

 of the two surface nets after a 15-minutes' haul on April 

 13th, 1907, at Station III. The one net contained 

 16 c.c. and the other 15'5 c.c, but these amounts were 

 made up very differently in the two cases. For example, 

 it will be seen that in the net C there were no Balanus 

 Nauplei and no immature Copepoda, while thousands of 

 both were present in B. Then, again, in B there were 

 very few adult Temora, while in C practically all the 

 Temora were adult. The lists will show other points of 

 difference. I may add that in the haul of the shear-net, 

 taken at the same place and time, there were 1,380 larva) 

 of Pectinaria in tubes, along with 5,400 Balanus Nauplei, 

 and many other organisms. 



Only omitting those organisms where less than ten individuals were obtained. 



