I92I. No. 4- THE PHVTOPLANKTON OF SOME XOR\VK(;iAN LAKKS. 49 



EXPLANATION OF PLATES. 



All the drawings are made to scale by means of the greatest model of the „Zeichen- 

 apparat nach Abbe" from Zeiss. The microscope used was the largest model of Zeiss, viz. 

 the I B. The objectives were mainly ÜD, and apochromate 3 mm. in conjunction with 

 ordinary and compensating eyepieces. 



The five photomicrographs were made by means of the apparatus of LErrz, with the 

 same microscope and the objective 16 mm. apochromate in conjunction with the compensating 

 oculars 8 and 12. Time of exposure varied from 5 seconds to 15, and the plates used 

 were the „Imperial", from the Imperial Dry Plate Compan^^ Ltd. 



Plate I. 

 Fig. I. Dcsniidiitiit Psctidostiiptouciiia W. «S: G. S. West. 

 Fig. 2. Sfaiirastntin brcvispiiniiii Breb. 

 Fig's ß — J. Siatirastntin jaculiferum W. West. Various two and three armed forms from 



various lakes. 

 Fig's 6^ J. Arthrocit'siiins Incus var. Hititfcldtii var. nov. 

 Fig. S. Spondylosiiini plaiiuiu IWolleI W. & (i. S. West. 

 Fig. Ç). Ccratiiiiu curvirostre Huitf.-Kaas. 

 Fig's 10 — 12. Ceratium hirnndiiiclla Ü. F. M. Fig's 10 and 12 are resting-spores from 



two lakes. 

 Fig's ij — 14. Gonatosygoii pilosiiiii Wolle. 

 Fig. I J. Cosiiiarimii coiitractiiin Kirchn. 

 Fig. 16. Xaiitliidimn antilopæuni var. Hebridariim W. & G. S. West. 



Central scrobiculations not indicated. 

 Fig. ly. Cosiiiariiaii dcpressttiii (Naeg.) Lund. 

 Fig. /<V. Cosiiiariitiii abbrcviatitiii var. plaiictoiiicitiii W. & G. S. West. 



The magnifications of the figures are: 

 Fig's I, 6, 7, S, I J, iS, I go diameters. 

 Fig's 2, 1 7, /<V/ diameters. 



Fig's ;, 4, /, /(), J2, 74, 16, 4QO diameters. 

 Fig. (f, igo diameter.-^. 

 Fig. 1 1 , jfSo diameters. 

 Fig. I ;. 2S0 diameters. 



Plate II. 

 Magnifications of the pluitomicrographs are; fig's 1 and 2, 108 diameters, fig. 3, 140 

 diameters. 



/. Plankton from I'aiisjo. 

 Species which are represented upon the plate arc : 

 Melosira gramdata, 

 Asterionella gracillima, 

 Tabellaria fenestrata var. asterioiielloides, 

 Pediastntm Boryaniim, 

 Gomphospharia laciistris var. compacta. 



