SEA-FISHERIES LABORATORY. 255 



II. — The Limits of Photo-Synthesis by Algae as the 

 Alkalinity Due to Their Action Increases. 



As was stated at the outset, our attention was first drawn 

 to the alkalinity question in relationship to photo-synthesis, 

 by the plaice disease in the spawning tank, and the presence in 

 this pond-water of an immense number of floating mono- 

 cellular algae with which minute green flagellata were also 

 present in great abundance. It was found then, in April 1912, 

 that the alkalinity of the pond-water was very considerably 

 higher than natural sea-water. 



The diatom outburst of the Spring had not yet appeared 

 and the alkalinity of the Bay water was low; on the other 

 hand it was found that the alkalinity of one portion of the pond 

 (which is separated into two parts by a wall and sluice) was 

 such that it required 3-3 c.c. of centi-normal acid to neutralise 

 100 c.c. to phenol-phthalein, and the other portion of the pond- 

 water required 3-8 c.c. of centi-normal acid in a similar titration. 

 As may be seen by comparing with the table given in Section 

 I, these figures are above normal for fresh sea-water, and 

 the pond- water was therefore in a pathological condition with 

 regard to alkalinity. 



The experiments of Loeb, and of Moore, Roaf and Whitley 

 mentioned in Section I., indicate that such alkaline water 

 would have a stimulating and in-co-ordinating action upon 

 cell-division. In fact the amount of increased alkalinity 

 would be just that which increases cellular activity. Given 

 a provocative cause of any kind such as a bacterial infection, 

 the conditions therefore were just those which would aid such 

 an ulcerative disease as that from which the plaice were dying. 



The pond-water was examined again for alkalinity and 

 contrasted with the alkalinity of freshly taken water from 

 Port Erin Bay in November, 1912 ; the results arc shown in 

 the following statement : — 

 B 



