14 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



The Hensen closeable net (Petersen's modifica- 

 tion) and the weighted open net were lowered to 

 about the same depth, but gave, when worked 

 together for the same time, in most cases very different 

 results. The two open surface nets (old and new) 

 were worked side by side, and although they were of 

 exactly the same size, and differed only in the age of the 

 silk of which they were formed, the catch was in most 

 cases very different. These differences were on some 

 occasions obvious to the eye when the net was emptied 

 on board ship ; but all the gatherings, carefully preserved 

 by Mr. Chadwick, have since been measured and worked 

 over by Mr. Andrew Scott, who has kindly supplied me 

 with his detailed lists. It is from these that I quote the 

 following examples. 



The gatherings varied in quantity from 0'5 to 40 

 c.cm., although all were as nearly as possible 15 minutes' 

 hauls. In some cases the plankton seemed to be fairly 

 evenly distributed between surface and deeper waters, 

 while on other days great differences existed, e.g., off the 

 Calf Island, on August 10th, the surface net and the net 

 towed at seven fathoms gave the same amount of 

 material; while at the same spot, on August 13th, the 

 surface net gave 8 c.cm. and the net at ten fathoms 

 32 c.cm., and the following day, at the same spot again, 

 the surface net had only 3*5 c.cm. and the net at ten 

 fathoms 40 c.cm. 



Even in cases where the surface and deeper hauls 

 were not very different in quantity, a marked difference 

 in quality was sometimes visible to the eye at the time, 

 and this has since been corroborated by Mr. Scott's 

 examination, e.g., on August 31st, off the Stack of Calf, 

 surface, 8 c.cm.; five fathoms, 13 c.cm.; ten fathoms, 

 14 c.cm. Mr. Scott remarks: — "Larger number of 



