366 NATURAL SCIENCE. juNfi. 



superintendent, dealing with methods and apparatus. (Btdl. III. 

 State Lab. Nat. Hist., Vol. v.) Owing to the shallowness of the 

 water in the district investigated, it was found impossible to carry 

 out the collection of plankton for quantitative determination in the 

 usual way, i.e., by vertical hauls of the plankton net. A method of 

 oblique hauls was consequently devised and used for some time, but 

 it appears to have been rather troublesome in practice, and was 

 abandoned in favour of the pumping method. Although collections 

 of plankton organisms have been previously made by pumping water 

 through a net, to the Illinois Station belongs the credit of having first 

 developed this method for use in quantitative work. The advantages 

 claimed for this method over those relying upon the drawing of a 

 net through the water are, mainly, greater accuracy and wider appli- 

 cation ; for in the first place the exact volume of water passing 

 through the net from the pump can be exactly ascertained, whereas 

 with a net hauled through the water this amount can only be 

 calculated approximately, and secondly, the collection of plankton by 

 means of a pump and hose can be carried on in very shallow water, 

 and even among masses of vegetation. There seems no doubt that 

 the introduction of the pumping method is an important departure 

 in plankton investigation. We can only see one theoretical objection 

 to its use, namely, that the water sucked up by the pump at any 

 particular level does not wholly come from that level but also in part 

 from higher and lower levels. This is probably, however, a point of 

 little practical importance in the majority of cases. Nevertheless we 

 do not think that the pumping method will altogether supplant the 

 earlier practice, for, in addition to its much greater initial cost, the 

 new method demands the attention of two men, one to work the 

 pump and the other to haul in the hose, and further, it could not be 

 easily applied to very deep water owing to the large amount of hose 

 required. 



Another important modification introduced into the plankton 

 work at the Havana Station has been the employment of a centri- 

 fugal machine for rapidly precipitating the plankton contained in the 

 collections, instead of allowing it to settle of its own accord for 

 twenty-four hours. This innovation not only saves time, it gives 

 more reliable results than heretofore. It was found by experimenting 

 with the same collection of plankton that the settling method gave 

 results differing from one another by as much as 30 per cent, in 

 extreme cases, whereas the action of the " centrifuge " was quite 

 uniform, the plankton always being subjected to the same amount of 

 compression. 



We trust that it will not be long before we see similar investiga- 

 tions being carried on in our own country. The Lancet, commenting on 

 our recent articles directed to this end, remarks with truth : " The 

 movement is surely a worthy one, and in the interests of science and 

 even national affairs should be supported." Our reinvigorated con- 



