1898] NOTES AND COMMENTS 219 



sesamt's, here exhibited ; and on April 20, another egg produced 

 P. octaria-nataJcnsis, also shown. Mr V. (!. 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. 



*o v 



Bread out of Air 



Sir William Crookes in his presidential address to the British 

 Association traversed a wide field, practical, physical and vsychi- 

 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 



