346 THE AMERICAN MONTHLY [Nov 



Plankton Nets. — The distribution of aquatic life from 

 season to season throug-hout the various zones of the plank- 

 ton in the larg^er masses of water of the g-lobe is an object 

 of study which has received considerable attention at the 

 hands of investig^ators during- the last decade. Theg-reat- 

 est difi&culty that has been experienced has been the need 

 of apparatus upon which the operator can rely to work sat- 

 isfactorily under all conditions and at all times of the year. 

 The nets that are usually used cannot claim these advan- 

 tag^es, inasmuch as they are always liable to damage and 

 loss when working- on a rocky bottom, and during the win- 

 ter months, when the plankton yields its most interesting- 

 results they are inadmissible in northern latitudes owing- 

 to floating- ice. The accuracy of the results, too, leave 

 much to be desired, as with the net it is not possible to de- 

 termine exactly the volume of org-anisms actually present 

 in a given quantity of water, nor is it practicable to deter- 

 mine the variousg-roups that are characteristic of the many 

 vertical zones or strata of water of which the plankton is 

 constituted. 



Plankton Pump. — For critical work, nets have had to be 

 discarded, and in place of them Dr. H. B. Ward has used 

 during- his recent investig-ations on the Great Lakes,alig-ht 

 weig-ht force pump which he calls the "plankton" pump, 

 and which can be carried about and operated by one per- 

 son. The cylinder of the machine is eleven inches long- by 

 three and a half inches in diameter, and it has a capacity of 

 three hundred and forty-seven and a half cubic inches per 

 stroke. It is essentially an ordinary force pump, save that 

 it has very finely g-round check valves, to which, it is be- 

 lieved, the accuracy of the working- of the apparatus is 

 larg-ely due. The pump is connected with the water by a 

 hose one and a half inches in diameter, the lower end of 

 which is adjusted to the various vertical zones of water by 

 means of an attachment to a floating- block. Most g-ratify- 

 ing- results have attended the use of this apparatus. It is 

 possible to measure with g^reat accuracy the amount of 

 water filtered. Collecting- can be carried on without any 

 disturbance of the water,and water can be drawn from any 



