60 



YVES B. PLESSIS 



Upper tank 



Figure 3. — Type of permanent siphon ; A, flared opening of the siphon, capable of accommodating a 



screen ; 1, upper tank ; 2, lower tank ; E, air opening. 



is fixed there by means of a vinyl ring. 

 This has enabled us to separate, from one 

 tank to another, very small animals which, 

 without that precaution, would have 

 passed through the siphons. These fun- 

 nels are preferably positioned in such a 

 way that their opening is at the bottom 

 end and as far away as possible from the 

 walls of the tank so as to reduce the risk 

 of the deposition of sediments. 



The level of the upper tank is regulated 

 by the height of the swanneck C; the level 

 of the lower tank is determined by its out- 

 let siphon which does not appear in the 

 drawing. 



It is helpful to have a supply of siphons 

 of this type. In order to clean them, it 

 is sufficient to place them, from time to 

 time, in a hypochlorite solution to soak, 

 and to rinse them well before use. When 

 the siphons do not have screens, a sulpho- 

 chromic mixture is preferable. 



•2. Capillary- priming s i p h on s. — We 

 have perfected a siphon the curved part 

 of which is so narrow that capillarity may 

 be able to prime the system even before the 

 water reaches the point of overflowing 

 (figs. 4, 5, G, and 7) . By duplicating our 

 piping system of permanent siphons with 



