492 DEPARTMENT OF THE NATAL SERVICE 



The following species were found: — 



Achnanthes twniata Grun., abundant, with resting spores 

 AmpJnprora hyperborea (Grun.) op^i co. 



Bacterosira fragilis Gran. 

 Bidclulphia mirita. (Lyngb. ) 

 Chwtoceras atlanticum. Cleve. 



compressum. Lander. 

 criophilum. Castr. 

 debile. Cleve. 

 decipiens. Cleve. 

 diadema. (Ehrbg.) Gran. 

 scolopendra. Cleve. 

 teres. Cleve. 

 Detonula confervacea. Cleve. 

 Eucampia groenlandica. Cleve. 

 Fragilaria cylindrus. Grun. 



oceanica. Cleve, predominating, with resting spores 

 Navicula pelagica. Cleve. fpoies. 



septenirionalis. Oestrup, abundan 

 Vaiihaeffeni. Gran. 

 Nitzschia closterium. W. Smith. 



frigidki. Grun. 

 Pleurosigma Stuxbergi. Cleve et Gran. 

 IZhisosolenia hebetata (Bail.) f. semispina, Hensen 

 Thalassiosira bioculata. (Grun.) 



gravida. Cleve, with resting spores. 

 hyalina. (Grun.) 



Nordenskioldi. Cleve, predominating. 

 J halas.siothrix longissima. Cleve et Grun. 

 Dinophysis granulata. Cleve. 



No such quantitie.s of diatoms were found in any of the quantitative samples from 

 June to August, and the species of diatoms which characterize the rich spring plank- 

 on ^re only found at some few stations in the gulf of St. Lawrence (stations 10 and 

 Vol V } \ '^ ^""^ ^''^^ *^^'^ ^" ^^^^^'^ quantities, and restricted to the 



ha"t theTh " ^r'y\''' '' ^' ^- ^^P'^- ^^^°"^ ^^"^ -^ -^y presumably conclude 

 of Tut f^l^'''''^l''^'^'^' -^P""^ plankton has already disappeared by the middle 

 of June or has sunk down to deeper water layers, whore remains of it are found for 

 the most part with resting spores. ^uunu, lor 



Cruise of the "Princess '^ June 9 to 15 (Table 1 (a), (b), and (c). 



The plankton samples from the cruise of the Princess, June 9 to 15, 1915 dis- 

 tinctly show that the development of the pelagic diatoms at this season has passed it^ 

 annual maximum. In the first place the markedly Arctic species, mentioned above, 

 have sunk down to the deeper water layers, where we may certainly presume that they 

 will no longer find conditions suitable for their further development, and have to a 

 considerable extent formed resting spores. But in addition to this, we find thaJ a 



and CJ. lacznwsum which somewhat later must have replaced the Arctic species is 

 now a ready declining. These species we find more particularly at the stat on 



rran -tv -n ib^^'^'^"" l' '' 'V ^^' ''^- ^^^^^ '^'^^ are Hkewise not found 



necre? T J r ^""^"'f ^^V^'^ ^"^" '''' ^^^"^ ^« deep dowia as the Arctic 



species. I heir maxima lie, as the table shows.— 



At station 3, at 20 m. 

 5, at 10 m. 

 " 10, at 0-25 m. 



12, at surface, but small quantities. 

 25, at 30 m., but sparsely. 



The stations where they are found nearest the surface (stations 10, 12) have lower 

 surface temperature than the places where the diatoms had almost or entirely dis- 



menced in these species also. 



