110 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



the highest point of L should be higher than the bend of the siphon 

 tube H. 



Aeration of Aquaria.* — 0. Thilo describes the following apparatus 

 for ventilating aquaria (fig. 16). A piece of rubber tubing of 2-3 mm. 

 bore and 30 cm. long is drawn through the tube of a glass' funnel so as 

 to leave the upper portion of the rubber tubing sticking out of the 

 funnel tube ; into the lower end of the tubing is pushed a piece of 



Fig. 16. 



metal tubing, and on to the free end of this tube is fixed a rubber tubing 

 of about 4-5 mm. bore, and the end of this rubber tube is pulled over 

 another metal tube E, (fig. 17). The funnel is suspended under a tap, 

 and water is allowed to drip into it ; the air in the tubing will be driven 

 into the aquarium, on the floor of which rests the tube R. The author 

 finds it is necessary that for a depth of 50 cm. of water in the aquarium, 

 the funnel should be at least 150 cm. above the floor of the aquarium. 

 It is also useful to place a perforated shield over the tube R in order to 



* SB. Gesell. Naturf. Freunde, 1906 (May) p. 139. 



