28 



PROF. W. A. HBRDMAN : COMPARISON OF SUMMER PLANKTON 



a few Sagitta, a few Echinoderm Plutei and Polychset Larvae, Ceratium 

 tripos, and some Diatoms, chiefly RIdzosolenia semispina. But the bulk of the 

 gathering is, in all cases, Calanus helgolandicus, and that gives it a charac- 

 teristic appearance which can be seen as soon as the net comes up. We have 

 in all eight vertical hauls taken during July in the years 1907, -08, -09, 

 and also a surface gathering taken at the same locality on July 28th, 1908. 

 This surface gathering is, however, of an entirely different character from 

 the vertical hauls. It is greenish in colour, and of fine flocculent appearance, 

 and is in constitution a phyto-plankton (see fig. 4) almost entirely composed 

 of Diatoms, chiefly species of Ehizosolenia. There are also a few Peridinians, 



Fig. y. — Mouotonic Zoo-plankton samples, one oi wliicli shows Calanus. 



and a very few small Copepoda, but the larger Copcpods characteristic 

 of the vertical hauls are entirely absent. 



A vertical haul from 83 faths. taken off Mt. Erins, further up Loch Fyne, 

 on that same date in July, 1908, shows the same type of gathering as the 

 vertical hauls off Skate Island. 



It is clear that the Calanus population extends in the deep water along the 

 length of Loch Fyne, as hauls taken at various points in Upper Loch Fyne, 

 both in 1908 and 1909, from depths of 54-70 faths., show the same kind of 

 gatherin gas those off Skate Island, On the other hand, in working down 

 the channel towards Bute, Arran, and Kilbrennan Sound, we find that the 

 gatherings are of a more varied nature. One off Sannox, Arran, on 

 August Ist, 1910, from 70 faths., is a mixture of phyto- and zoo-plankton, 

 and does not contain the large Calanoid Copepoda in any quantity. A haul 

 taken o& the Cock of Arran at the same season in the previous year, from a 



