322 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



number of different genera and species, and for com- 

 parison with it a polymiktic plankton formed largely of 

 Diatoms, but containing also Polychaet larvae, Cirripede 

 nauplii, and other animals. On Plate B all the figures 

 show examples of uniform monotonic planktons, both 

 plant and animal, the two upper being characteristic 

 Diatom gatherings and the two lower being from hauls 

 through swarms of Copepoda. vSuch Diatom gatherings 

 are commonly found in April off Port Erin, and the 

 Copepod swarms later in the summer. 



We have several times found enormous but quite 

 localised swarms of C alarms helgolandicus (Plate B, fig. 4) 

 inside Port Erin Bay in July or August, and have filled 

 jars with pure gatherings of this one species which have 

 served to supply the University students with specimens 

 of this typical large Copepod for several years. Large 

 Acartia swarms like that from which fig. 3 was photo- 

 graphed have occurred late in April, in August and in 

 September, and other common species of Copepoda have 

 also occurred on occasions in large swarms, both in Port 

 Erin Bay and in the open sea outside. 



When we obtained 2,300 Sagitta in one haul of the 

 shear net on March 31st, '09, that was undoubtedly an 

 unusual swarm. The animal was not generally distributed 

 through the neighbouring parts of the sea in that density, 

 since a similar haul of the same net on the following day 

 gave 245 specimens. We might quote many similar cases, 

 but it seems unnecessary to multiply instances further. 

 We may take as a final example pelagic fish eggs, in 

 regard to which the statement has sometimes been made 

 that they are uniformly distributed oyer very wide areas. 

 Our experience certainly does not support such a view. 

 The numbers obtained per haul are most irregular. Over 

 large areas very few floating eggs may be obtained, even at 



