290 PLANKTON STUDIES IN RELATION TO 



S.W, of Lizard, where a catch of 500 mackerel was made. The water 

 appeared to be of a distinctly different type of a clear green tint. This 

 was considered by the fishermen to be in every way suitable for the 

 presence of shoaling fish. The examination of the sample showed 

 the following points. Zooplankton was in excess of phytoplankton. 

 This condition, however, was not brought about by a very pronounced 

 decrease in the quantity of diatoms, but by the increased number of 

 Copepods. Calanusjinmarchicus, which was rare in the former sample, 

 was common in the present one. 



Between Samples 24 and 26, Plankton Tables, the former of which 

 was taken by fishermen in " green water " and the latter in " blue," and 

 from widely dissimilar positions, viz. 35 miles S.S.W. of Newlyn and 

 18 miles south of the Lizard, on May 5th and 10th respectively, there 

 did not appear to be any striking points of difference. In each zoo- 

 plankton was in excess of phytoplankton. The relative quantity of 

 phytoplankton of the " green water " sample, however, was greater 

 than that of the " blue water," although in the latter there was a slight 

 quantity of Fhaeocystis globosa, which was absent from the former. 

 A greater variety of diatoms was observed in the " blue water " sample 

 than in the " green," the higher proportion in the latter, already re- 

 ferred to, being due to two species, Rhizosolcnia alata and B. styliformis, 

 both plentiful. 



In the main the zooplankton observed in each sample was similar. 

 The Copepod Temor« ^OTir/icomzs, however, occurred in the "blue water" 

 sample, whilst it was absent from the " green " ; but the more eastern 

 distribution of the species described under a former heading would 

 probably account for its absence in this sample of more western origin. 



Samples 32 and 33, Plankton Tables, may be compared in a similar 

 manner. They are taken later in the season, but present no striking 

 dissimilarity. 



No verified observations were taken in " grey water " except Sample 

 23, which, as stated in a footnote, would appear to be unreliable. 



" Yellow Water." — In 1906, on May 20th, a sample was taken by 

 fishermen in such water 40 miles S.W. of the Bishop. Unfortunately, 

 however, the bottle containing the sample was broken in transit, and in 

 consequence the exact nature of the plankton was difficult to deter- 

 mine. It appeared, however, to be composed very largely of the two 

 Copepods Calanus finmarchicus and Pseudocalanus elongatus, and from 

 the appearance of the remains it seemed to have been a very bulky 

 sample. 



This sample formed the sole observation from " yellow water " 

 furnished by fishermen during 1906 and 1907. Throughout May, 1907, 



