TBANSACTIONS OF SECTION D. 717 



relaxed its exertions and the locusts again bred and multiplied, until, by the time of 

 the British occupation in 1878, they had so increased as to cause anxiety for the 

 future. Acting under local advice, the Government attempted to keep them down 

 by collecting and destroying their eggs. This operation was continued for three 

 years on a vast scale, involving a heavy outlay, but without success, for, although 

 this method was attempted on a scale almost without precedent, the locusts con- 

 tinued to increase with alarming rapidity, until in 1882 they swarmed throughout 

 the plains, and in spite of various attempts to destroy them the damage sustained 

 by crops was very great, and probably did not fall short of 80,000/., or from 15 to 

 20 per cent, of the value of the crops on the infested area. 



In 1883 and 1884 operations against the locusts were limited exclusively to 

 attacliing them in the crawling stage by the apparatus known as the Cyprus system 

 of screens. These were formed of canvas and were stretched across the line of 

 march, so that the onward progress of the locusts was arrested, and they were then 

 diverted into pits carefully trapped, from which there was no escape. By the opera- 

 tions of these two years the power of the locusts was so effectually destroyed that 

 no damage whatever has been sustained by the crops during the past five years ; 

 and although it is still necessary to watch the locusts and prevent their increase, 

 this is now done at a comparatively small annual outlay — and their numbers have 

 so steadily decreased year by year as to warrant the hope of their final extermi- 

 nation. 



In submitting this paper to the Association the author was influenced by the 

 hope that some of its members might be able to throw light on problems which 

 (although they have received from him considerable attention) he has been unable 

 hitherto to solve in a definite and satisfactory manner. The chief of these are : — 



1. The rate of increase and the number of eggs deposited by different varieties 

 of locusts. 



2. How is it that some varieties possess the migratory instinct in an eminent 

 degree, while others closely allied in outward form appear to be altogether devoid 

 of it? 



3. AVhat are the laws that determine the direction of the march or flight of 

 migratory locusts ? 



2. 071 the Fauna of the Firth of Clyde. By W. E. Hotle, M.A. 



3. On a Deep-sea Tow Net. By "W. E. HOTLE, M.A. 



4. On some Points in the Natural History of the Coral Fungia. 

 By J. J. Lister, M.A., F.Z.8. 



The coral fungia is abundant in shallow water on the reefs of the island of 

 Mah6 in the Seychelles Islands. Many examples of the fixed stocks were obtained. 

 These show the "disc in all stages of growth, from the young stocks with six primary 

 septa conspicuous, to the stage in which separation of the disc takes place by ab- 

 sorption in a plane which is situated where the stalk is beginning to widen out into 

 the disc. 



The disc, when set free, has a scar on its under surface, exposing a section of the 

 thecal wall, septa, trabeculfe and the soft tissues investing them. Calcareous 

 matter is subsequently deposited over this, obliterating the scar. 



A similar section is exposed on the summit of the stalk. From this a new disc 

 is formed by growth of the septa and other structures. An early stage was ob- 

 tained in which delicate fluted laminas had been formed on the edges of the septa 

 just projecting above the scar surface. These grow higher and higher and a new 

 thecal wall is built up just within the margin of the thecal wall of the stalk, and 

 thus a new disc is produced. This again is set free, when it is fully formed, at a 

 plane above that at which the first disc was separated ; and the repetition of the 

 process gives rise to the jointed appearance of the stalk. 



