1898] NOTES AND COMMENTS 219 
sesamus, here exhibited; and on April 20, another egg produced 
P. octavia-natalensis, also shown. Mr F. G. Richmond of Braunton, 
Devon, had arranged some aquaria containing various species and 
hybrids of trout and salmon. The exhibit of the Marine Bio- 
logical Association was of interest, not so much for the species 
shown as for the illustration it afforded of success, under the 
most difficult conditions, of keeping marine animals of various 
kinds alive by the constant circulation of the water. There 
were five shallow wooden tanks and about 400 gallons of sea- 
water was used. The water entered the tanks from a small 
upper reservoir by means of glass siphons, and after passing 
through them collected in two lower reservoirs, from which it 
was periodically pumped into the upper: one again. The pump 
used was an ordinary semi-rotary yacht pump. Most of the fish, 
as well as many of the invertebrats, had been living in a healthy 
condition in the tanks for some two weeks previous to the opening 
of the exhibition, and there had been comparatively few deaths. 
Naturalists were also glad to have the opportunity of seeing in 
operation the ingenious plungers devised by Mr E. T. Browne and 
Dr E. J. Allen, and worked automatically by means of the fresh- 
water supply filling a can that was intermittently emptied by a 
siphon. Such a plunger keeps the sea-water in a bell-jar aquarium 
in constant movement, and serves to keep medusae alive and to rear 
the larvae of marine animals to the adult stage. 
BREAD OUT OF AIR 
Str WILLIAM CROOKES in his presidential address to the British 
Association traversed a wide field, practical, physical and psychi- 
cal, in each department applying or suggesting the application of 
the most recent advances in modern physical research. 
Starting with the question of late so much mooted, of the 
wheat -supply of these islands, intimately connected with the 
wider question as to the possible insufficiency of the wheat-supply 
of the whole world at no distant date, Sir William showed that 
whereas the consumption of wheat was increasing, the amount of 
land available for its production was strictly limited, and that 
already those limits were nearly reached. It is therefore necessary 
to increase the fertility of the land by means of nitrogenous. 
manures. Unfortunately that special sanitary appliance which is 
the glory of our country,and which she has presented to all parts of 
the civilised world, has the disadvantage of wasting, in this country 
alone, “‘ fixed nitrogen to the value of no less than £16,000,000 
per annum.” But even if we relinquish the system that Liebig 
stigmatised as “a sinful violation of the divine laws of nature,” we 
shall not repair the mischief already done. Already the world’s 
