1894.] Presents. 441 



From these observations it is also clear that the sounds produced 

 by these fishes are not caused by the expulsion of air through the 

 ductus pneumaticus, as erroneously assumed by us on pp. 298 and 

 p. 301 of our memoir, but are caused by the vibration of the air 

 within the air-bladJer, which is set in motion either by the " elastic 

 spring " apparatus, or by the extrinsic muscles. 



The investigations of Dr. Sb'rensen seem to show that, under 

 certain conditions, the " elastic spring " mechanism, and the paired 

 extrinsic muscles of the Pimelodince, are structures subordinate to 

 sound production, anc? are not, as we suggested, related to any method 

 of adjustment to varying hydrostatic pressures. Had we appreciated 

 this fact earlier, we should have modified certain of the tentative 

 conclusions suggested on pp. 298 301 of our memoir. On the pre- 

 sent occasion we wish to draw the attention of those interested in 

 the subject to Dr. Sorensen's researches, and at the same time to 

 express our regret at the injustice we have unintentionally done 

 him. 



The Society adjourned over Ascension Day to Thursday, May 10. . 



Presents, April 26, 1894. 

 Transactions. 



Buitenzorg : Jardin Botanique. Annales. Vol. XII. Partie 1. 

 8vo. Leide 1894. The Director. 



Edinburgh : Botanical Society. Transactions and Proceedings. 

 Vol. XIX. Pages 233-636. 8vo. Edinburgh 1893. 



The Society. 



Haarlem . Musee Teyler. Archives. Vol. IV. Partie 2. 8vo. 

 Haarlem 1894. The Museum. 



Irkutsk: East Siberian Section, Imperial Russian Geographical 

 Society. Annual Report. 1892. [Russian.] 8vo. Irkutsk 

 1894. The Society. 



Kazan : Imperial University. Scientific Notes. [Russian.] 1894. 

 No. 4. 8vo. Kazan. The University. 



Kew : Royal Gardens. Bulletin of Miscellaneous Information. 

 1894. No. 88. 8vo. London. The Director. 



London : Aristotelian Society for the Systematic Study of Philo- 

 sophy. Proceedings. Vol. II. No. 3. Part I. 8vo. London 

 1894. The Society. 



City and Guilds of London Institute. Report to the Governors, 

 1894. 8vo. London. The Institute. 



Marine Biological Association. Journal. Vol. III. No. 2. 

 8vo. London 1894. The Association. 



Marseilles: Faculte des Sciences. Annales. Tome III. Fasc. 4. 

 4to. [Marseille 1893.] The Faculty. 



