TRANSACTIONS OF SECTION D. 49] 
fauna of Bengal and other parts of the Indian Empire, it would be necessary to 
undertake a survey of the latter. A little later a substantial increase in the 
scientific staff of the Indian Museum made it possible greatly to extend our 
activities, and, almost insensibly, a survey of the kind has actually commenced, 
Colonel Alcock’s work on the Decapoda forming an excellent standard and basis 
for comparison. In one point we have even attempted to improve upon that 
standard, namely, in paying very particular attention to the bionomics of the 
animals described. With the zealous co-operation of numerous correspondents 
in different parts of the country, and more especially of the Assistant Super- 
intendents of the Museum, Messrs. Stanley Kemp, B. L. Chaudhuri, and F. H. 
Gravely, of our honorary assistants, Captain Seymour Sewell and Mr. T. 
Southwell, and of Mr. E. Brunetti, the work is now proceeding apace. Already 
an account of the sponges, polyzoa, and hydroids has been published in the 
“Fauna of British India,’ and the Indian representatives of several of the smaller 
groups have been discussed in the ‘ Records of the Indian Museum.’ Mr. Kemp 
has commenced a detailed account of the Decapoda Macrura, and Mr. Chaudhuri 
a revision of the fish of Northern India, while Mr. Gravely hopes shortly to 
describe the interesting flat-worms of the group Temnocephaloidea. Among 
the most interesting specific discoveries already made in connection with the 
stuvey are those of an Indian freshwater medusa of the genus Limnocnida, 
a new type of Temnocephaloidea allied to the European Sewtariella, a Rhizo- 
cephalon from the hills of the Andaman Islands, a species of NXiphocaridina 
(Atyide) hitherto only known from New Zealand and the Chatham Islands, 
several interesting aquatic oligochetes, and a considerable number of new species 
of fish. 
Lantern slides of some of the more interesting types were shown. 
5. The Plankton of Lough Neagh, Ireland. 
By W. J. Daxiy, D.Sc., F.L.S., and M. Latarcuse, M.Sc. 
The following is a brief account of a few interesting results of a somewhat pro- 
longed study of the Lough Neagh plankton. The research was commenced in 
1910, and was aided by grants from the Royal Society and the Royal Irish 
Academy. The complete Paper will appear shortly in the ‘Transactions of the 
Royal Irish Academy.’ The investigation extended over a year, and during 
this time catches were made quantitatively at regular intervals. It is therefore 
the first quantitative fresh-water plankton investigation to be made in the British 
Islands, and the first detailed zoo-plankton investigation of any kind to be carried 
out over a long period in a British lake. 
The water of Lough Neagh is extremely rich in plankton, and a comparison 
with the Irish Sea shows that there is far less plankton present in the latter, 
taking the quantity for the whole year in both cases, and an equal volume of 
water. The conditions, on the whole, differ greatly from those observed during 
Sir J. Murray’s investigations of the Scottish lochs, and the researches of the 
Messrs. West on English lakes. As a matter of fact, the Danish lakes resemble 
much more closely Lough Neagh in the character of the plankton present. Both 
the phyto-plankton and the zoo-plankton of Lough Neagh are made fip of Arctic 
and Central European species existing side by side. The distribution records are 
perhaps amongst the most valuable and interesting of the results. 
The authors cannot accept the Wesenberg Lund-Ostwald theory that seasonal 
variations in planktonic organisms are due wholly to changes in the viscosity of 
the water. The changes observed in the plankton species of Lough Neagh are of 
the usual two kinds, form and size. The Wesenberg Lund-Ostwald hypothesis 
assumes that a reduction in size takes place in the summer months, so that by a 
relative increase in superficial area the organisms can still remain buoyant though 
the viscosity of the water has decreased. Similarly, spines or other excrescences 
will be developed when the water is most warm. The authors consider that :— 
(1) It is characteristic of organisms of colder waters to be larger, whether 
planktonic or benthic and fixed. 
(2) The seasonal variation is more likely determined by other factors—as 
experimentally shown by Woltereck—and in some cases this variation merely 
