408 !•:. J. ALLEN AND L'. W. NELSON. 



from shore, was placed in a tall Leil-jar fitted with a 

 " phinger/' wliicli keeps the water in constant movement 

 (' Jonrn. Mai-. Jiiol. Assoc./ vol. v, p. 170). The water was 

 treated with Miquel's solutions in normal pioportions, and a 

 considerable quantity of plankton taken with a fine-meshed 

 net (150 meshes to the inch) was added, say 10 or 20 c.c. of 

 a moderately rich sample of tow-netting. The experiments 

 were made during tlie spring and summer months, and the 

 general course of events has been the same, with a certain 

 amount of difference in detail according to the nature of the 

 plankton present at the time. 



During the fii'st two d<i,ys the water often became cloudy, 

 owing to the rapid multiplication of small Hagellate infusoria, 

 though this was not always the case. Plankton copepods and 

 other animals gradually died off, though some survived for as 

 long as a week or ten days. The plankton diatoms, on the 

 other hand, generally multiplied rapidly during the early 

 days of the experiments, the first to become abundant in the 

 body of the water being usually Skeletonema costatum, 

 which at the end of a week might be so thick that a number 

 of chains could be seen in every drop of water examined with 

 the microscope. Along with the Skeletonema were found 

 other plankton diatoms, such as Lauderia borealis, 

 Chc"etoceras (two or three species), Biddulphia mobi- 

 liensis, Ditylium Brigh twellii, and in nearly every case 

 Thalassiosira decipiens. These latter diatoms were pre- 

 sentin moderate numbers only, when the Skeletonema was at 

 its height, but as the Skeletonema died down they increased 

 in quantity. At the same time Nitzschia closterium com- 

 menced to appear, both amongst the precipitate on the bottom 

 of the jar and in the general body of the water. Small green 

 flagellates often began lo get numerous also at this stage. 

 The true plankton diatoms were at their height about a fort- 

 night after the experiments were started. At this time a 

 great many diatoius of all kinds were to be found amongst 

 the precipitate at the bottom of the jar, Asterionella 

 japonica and Coscinodiscus excentricus being often 



