124 



Littoral forms: 



I'lriira.nis proctirvaiits liirge. 



ricnro.riis dciificiilnfiis Birge. 



Enryccrciis Unnellatus O. F. JM. 



Acroijcms harpae Baird. 

 The following- genera were represented by at least one species each. 

 Alalia, Gniptohbcris, and Siniocrphaliis. 



Cypris and CorciJira larvic were fonnd in some of the catches. 



KCniVFAiA. 



Vowv lucinlMM-s (if tJiis gi'oup wei-e specifically identified, Triarthrd 

 IdiKjisctd, [inirai (-(jchlrai is. Aiiiinii aciilcdtd. and Noflioica Inngispinii. The 

 other mcmlicrs of the gronp liclongt'd to the genera AKplniicliiKi, I'oli/aiflini, 

 and \l(isti<i)t<-trcii. 



CHANGE IN (H'ANTITY OF PLANKTON. 



These ohsci-xations covered too l>ri<'f a period, .inly 10 to September .3, 

 to sliow mnch concerniug tlic increase nr (h'crease of the varions plankton 

 constif ntents. In general, it may lie said tliat tliei-e was comparatively 

 little change. There was ajiparently a slight in( re.-ise of the phytoplank- 

 ton, dne mainly to an increase of Clatlii-oeystis. Only two forms of the 

 Crustacea showed any change. Dnring August, tliert' was a perceptible 

 increase of Diaptomus and Cyclops. They were found to be tAvice as 

 numerous the fii'st of SeiUember as the last of .Tidy and first of August. 



DIURNAL MOVEMENT. 



Kpisclnird /(/c/rs-Zz/.s'. -Tliis form was not found regularly in the day 

 catches as it was iiresont in oidy six of tlie twenty day series. On these 

 six occasions it was confined to the thermocline, that is, between five and 

 seven meters. It was taken, however, in the surface catches of the six 

 night series. The time of its appearance at the surface varied from half 

 an hour to an hour and a half after sunset and it disappeared from the 

 surface about an hour before sunrise. In the all-night series of August 

 5-0, it was found in only one catch. This was ;it 1) p. m., live individuals 

 per 100 liters of surface water. In the all-night series of August 2T-2S, 

 it reached a niaxinuuu of l-tO per llXi liters at 8 p. m. 



