280 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



to be due to. an excess of Diatoms in (lie vertical closing 

 nets — thus showing thai the protophyta are more 

 abundant at that time in the lower layers of water. 

 Larger organisms such as Medusae, Sagitta, Copepoda, 

 Larvae and Fish Eggs are more abundant in the surface 

 and the weighted nets — and more in the latter than in the 

 former. We also find that, using similar open tow-nets, 

 a net towed at a depth of a fathom or so catches more 

 than one on the surface. At the time of the phyto- 

 plankton maximum in spring it seems from the evidence 

 of these various nets that the Diatoms are present in an 

 increasing ratio as one descends from the surface to at 

 least twenty fathoms ; but that the Copepoda and other 

 larger forms are most abundant in a zone within ten 

 fathoms of, but below, the surface — probably in some 

 cases only a fathom or two below it. For example we 

 may quote the following particulars from Form 28, April 

 13th, which is not an extreme case, as the Diatom 

 maximum is then past : — 



Surface nets. Weighted net. Hensen. Nansen. 

 (10-0 f.) (20-10 f.) (20-10 f.) 

 Total Diatoms ... 6,500 6,650 11,000 96,000 290,000 



Total Copepoda ... 1,970 1,880 3,180 66 335 



Here the Diatoms are clearly most abundant in the depths 



and thin upwards ; while the Copepoda are more abundant 



above and most abundant of all a few fathoms below the 



surface. Many of the Forms about this date show similar 



results. Later on, when the Diatoms have become much 



less abundant, the vertical closing nets bring up very 



little from the lower zones of water and are surpassed by 



all the other nets, e.g. — 



Surface nets. Hensen. Nansen. Weight. 



April 24— Station 1 205 15-5 05 2 16 c.c. 



24— Station II 7 15 3 5 17 5 c.c. 



25— Station III 55 4 -5 15 2 20 c.c. 



25— Station V 8 7*5 1 2-5 9"5 c.c. 



26— Station V 4 4 5 05 075 8 c.c. 



Aug. 21— Station 1 3 3 05 2 6'5 c.c. 



