474 TRANSACTIONS OF SECTION D. 



down the North and South Atlantic by the Canary Islands along a roughly 

 north and south line to Cape Town, and from thence along the Southern Ocean 

 on an east and west line to Fremantle in Western Australia. The managers of 

 the Blue Funnel line (Messrs. Alfred Holt & Co.) materially promoted this 

 work by most generously fitting up special discharge pipes with large taps on 

 both sides of the top deck, and by fitting up a large deck cabin on the 

 Ascanius as a laboratory for Professor Herdman. in which microscope work 

 could be conveniently carried on either l)y day or electric light. 



On the return journey three observers took part in tlie work. Professor 

 Herdman took a series of 32 samples through tlie Indian Ocean and Red Sea, 

 Dr. A. Holt collected 42 samples during parts of his homeward route by the 

 Malay Archipelago, Hong Kong, Singapore, and Ceylon : and Mr. P. G. Bailey 

 obtained for us 21 samples during his voyage by New Zealand across the Pacific 

 to San Francisco. We are very much obliged to Dr. Holt and Mr. Bailey for 

 this kind assistance. 



In addition to these 167 samples collected from most of the great oceans of 

 the world in the summer of 1914, we have also taken into consideration a few 

 former collections made by one of us, viz., (1) on a traverse to and from Cape 

 Town by the Atlantic route in 1905, (2) on a traverse of the Red Sea and 

 Indian Ocean to and from Ceylon in 1907, and (3) two or three other minor 

 collections which may be useful in filling up gaps between the larger series. 



The samples are now being examined systematically and exhaustively, and 

 it will be some time yet before we can make a detailed report ; but we think it 

 may be of interest to give now this preliminary account of the matter. 



So far as possible the conditions of collecting were kept constant, so that the 

 samples might be comparable with one another. It was calculated that during 

 the work on the Ascanius the amount of water running through the net was 

 about 10 litres per minute or 7,200 litres per twelve hours' gathering. If w-e 

 attempt to compare this volume of water strained with the amount that passes 

 through an ordinary horizontal or vertical plankton net of 34 cm. diameter at the 

 mouth we think it might on a rough appi-oximation be the equivalent of 100 

 yards of horizontal towing or 50 fathoms in a vertical haul. 



On looking at the volumes of the gatherings it is noteworthy how the amount 

 of plankton per haul drops in passing from coastal to oceanic waters. The first 

 gathering was practically across the mouth of the English Channel from the 

 Scilly Isles to abreast of Ushant, and was an ordinary typical English summer 

 plankton measuring 14'5 c.c. and consisting of many of the smaller Copepoda such 

 as Oithonn and Pseudoralnnvs with a few Centropages, and also a considerable 

 number of the Pteropod Limacivn. The fourth haul, thirty-six hours later, in 

 the Atlantic about the latitude of Lisbon, measured only 1 c.c. and contained, 

 in addition to a few species of the smaller Copepoda, oceanic organisms such 

 as Globigeriiia biilloides and Aconthomctra. 



A drop in the quantity of plankton per haul was noticed in passing from the 

 English Channel to the Bay of Biscay and a further drop in passing out into the 

 Atlantic off the coast of Portugal. During the next few days in the open 

 Atlantic north of the Canary Islands the following additional Copepoda were 

 noteworthy in the gatherings : Clausoralanus arcuicornis, Corycceus rostratus, 

 and C. gracilicaiida. Calocdlanus plumulosus, MicrosetcUa rosea, Ovccta subtilis, 

 PJriiromamma f/raclle, Liicictitia flavicorniSj and Sapphirtna nigromaculata. 



In the South Atlantic, between the Canary Islands and the Cape, at least 

 three species of Sapphirina (S. nigromaculata, S. Salpce, and another) occurred 

 frequently in the gatherings ; and other Copepoda that appeared south of the 

 Canaries were : Pleuromamnia grarih and P. ahdontinah, Vndeurhipta phiino.-ri. 

 Candacia pachydactyla, C. hispinosa and C. hipinnata, Metridia boecki, 

 Undinula vulgaris. Corycdi^is carinatus, Calocalunus pavo, and various species 

 of Macrosetello, EucJutta, Mirada, PoiHellopsis, Ijoh'docprn, and other.s — only 

 the more conspicuous forms are mentioned. 



The increase in volume of the catch on approaching Cape Town was well 

 marked — successive hauls being 2, 3, 4, 6'5 and then 11 c.c, and after leaving 

 the Cape they fell again to 5, 6, 64 and 4 c.c. 



On the day after leaving the Cape (July 13) the sea was very noticeably 

 blood-red in colour, and highly luminous at night. The gatherings were found 

 to contain large numbers of a small red Peridinian which was probably tlu? 



