288 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



forms and fish eggs are given in the preceding pages and 

 need not be repeated here. 



9. The Irish Sea contains a surprising number of 

 what are usually regarded as " Oceanic " species — not 

 merely as occasional visitants, but as normal and 

 continuous constituents of the plankton dining a great 

 part of the year. Amongst these may be mentioned 

 Chaetoceros densum, Coscinodiscus radiatus, Rhizosolenia 

 semis pina, Cerativm tripos, Peridinivm sp., Tomojiteru 

 onisciformis, Sagitta bipunctata, Pleurobrachia pilots, 

 Calanus helgolandicus, Anomalocera pattersoni, Acartia 

 dausi, Oithona shnilis, and Oikopleura dioica. Some of 

 these oceanic species seem, so far as we can judge from 

 the published records, to be more abundant and more 

 continuously present round the Isle of Man than they are 

 even in the western part of the English Channel. 



10. We have evidence from our closing vertical nets 

 that the 2one of most abundant life is not on the surface 

 but is generally a few fathoms below — say, usually, 

 between 5 and 10 fathoms. Samples of water from 5, 10 

 and 20 fathoms obtained with the " Mill " water bottle 

 support the above statement. But this conclusion was 

 arrived at, and could be established, quite apart from the 

 evidence of the vertical nets, from a comparison of the 

 Jesuits obtained by the weighted and surface open 

 horizontal tow-nets. 



11. At the time of the Diatom maximum in spring, 

 however, our closing vertical nets showed that these 

 Protophyta are more abundant in the deeper zones than 

 at the surface, and increase in density downwards to at 

 least 20 fathoms. 



12. In the case of some groups, e.g. Cladocera and 

 Oikopleura sp., the distribution is sometimes remarkably 

 regular, the same numbers being taken simultaneously 



