406 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



both fresh-water and marine plankton,* and most 

 planktologists will probably agree that there are such 

 " internal factors " affecting the occurrence and 

 quantity of the plankton independent of environmental 

 or hydrographic factors. 



The investigation of the plankton is a very special 

 study requiring exploring vessels at sea, laboratories on 

 shore and carefully trained biologists. Unlike the case 

 of hydrography, no information in regard to this subject 

 of investigation can be obtained from any other source. 

 But, on the other hand, it can, and ought to be, closely 

 associated with hydrographic observations and also with 

 the statistics of commercial catches. Hydrographic 

 observations and plankton samples and information in 

 regard to the fishing in the locality ought all, so far as 

 may be possible, to be obtained simultaneously. 



7. The International Work The plankton portion 



of the original programme devised by the International 

 Council entailed the quarterly collection (in February, 

 May, August and November) of plankton at a number 

 of fixed stations, by means of horizontal (at various 

 depths) and vertical hauls with nets of various mesh. 

 [The justness of the criticism then made that the 

 quarterly intervals were too long, and the fixed stations 

 too far apart, is now generally admitted.] 



In August, 1909, the International Council 

 resolved : — 



(i) " That plankton sample® should be collected by 

 means of vertical hauls at certain definite places as often 

 as possible (weekly or fortnightly), and that if research 

 steamers were not available, observations should be made 

 from lightships and inspection ships." 



(ii) " That quantitative methods should be employed 

 to a greater extent than formerly, that samples should 

 * See also, Herdman in Internationale Eevue, Bd. II, p. 124, 1909. 





