342 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



faths. (twice), 69-0 faths., and 73-0 faths. Coscinodiscus 

 concinnus occurred only in the G9-0 faths. haul; 

 Guinarclia flacdda only in one GO-40 faths. haul ; 

 Lauderia horealis only in the 73-0 faths. ; Ceratium furca 

 in one 60-40 faths., and one 40-20 faths. ; Trochiscia sp. 

 only in one 20-10 faths. haul. 



On another occasion, when hauls were made at 

 varying depths from 60 to 10 faths., and one from 60 faths. 

 to the surface, Oikoplewa was present in all the hauls up 

 to 10 faths., but absent from the haul from 60 faths. to 

 the surface. 



We have also observed how frequently the pictures 

 presented by the Hensen and Nansen nets differ, with 

 regard both to the number of species present and to their 

 vertical distribution. Thus, on April 8th, '09, at the mid- 

 channel station, the Hensen and the Nansen nets were 

 hauled as follows :— 60-40 faths., 40-20 faths., 20-10 

 faths., and 60-0 faths. Coscinodiscus grant was present in 

 the Hensen net in the 60-0 faths. haul only, and with this 

 evidence alone one would say it was present only in the 

 upper layers. But in the Nansen net it occurred in the 

 60-40 faths. haul only, thus giving grounds for supposing 

 that it was fairly uniformly distributed, but had escaped 

 the other hauls. On several occasions, when the Hensen 

 and Nansen nets have been worked together, one of them 

 has had species not represented in the other. 



Further, when the vertical nets are hauled to the 

 surface, it is often advisable to check their results by 

 comparing with the surface nets. Thus, on September 

 14th, '08, at Stat. IV, both Hensen and Nansen nets 

 hauled to the surface had missed the following species: — 

 Chcetoceros contortum, Rliizosolenia shrubsolei, R. stolter- 

 fothi, " Mitraria" Podon intermedium, Anomaloceta 

 jmttersoni and Microcalanus jousillus. This was observed 



