SEA-FISHERIES LABORATORY. 



311 



markedly, this same relative reduction of the plankton in 

 August. 



Our deepest vertical haul, off Sound of Rona, 140 

 fathoms, on August 15th, is perhaps the nearest to a 

 phyto-plankton of the whole series. There are as many 

 species of Diatoms as of animals present, and the number 

 of individuals of the former is, of course, many times 

 greater. A neighbouring haul, also one of the deepest, 

 taken the following day, off the north end of S. Rona, from 

 130 fathoms, is still more phyto-planktonic so far as 

 numbers go — containing, as it does, 90,000 individuals of 

 the Diatom Corethron criophilum. 



It may be of interest to have these two hauls given 

 here in full : — 



Off E. end of Sound of Rona, Aug. 15, 140 faths. 



Off S. Rona, 

 Aug. 16, 130 f. 



Zoo-plankton : — 



Calanus finmarchicus 1,200 



Pseudocalanus elongatus 6,200 



Oithona similis 1,000 



Metridia lucens 200 



Nauplii 2,600 



Thysanoessa inermis 1 



Sagitta 10 



Tintinnidae 1,600 



Gastropod larvae — 



Phyto-plankton : — 



Peridinium spp 400 



Asterionella japonica — 



Biddulphia spp — 



Chaetoceras breve 400 



„ criophilum 7,800 



debile 7,200 



,, decipiens 800 



teres 600 



Corethron criophilum 20,000 



Coscinodiscus radiatus 600 



Rhizosolenia semispina 600 



1,000 

 4,000 

 1,800 

 100 

 4,200 



6 



3,600 



200 



400 

 200 

 400 



8,000 



800 



2,600 



90,000 



400 



1,400 



Most of the other vertical hauls contain only a few 

 hundreds or thousands of Diatoms in place of the millions 

 present on some former occasions. 



