342 



H. C. VAN DER HEYDE 



TABLE 1 



Analogous results have been obtained by Elsa Kreuger" in a 

 series of very careful experiments. This author studied, more- 

 over, the rate of oxygen consumption, and could show that after 

 a very rapid decrease in oxygen content in the beginning a kind 

 of equilibrium is reached after a while between the tracheal air 

 and the air of the reservoir, so that after that the curve proceeds 

 much less steeply. 



2. The*animal really expires when it opens its breathing cleft 

 at the surface. I could prove this fact which had already been 

 made very probable by the movements of the droplet in the 

 apparatus of figure 1 in using the following little apparatus, 

 not previously described (fig. 3). It simply consists of a beaker 

 covered by a flat cork. A space. A, has been made in the center 

 of the cork^i in which a bubble of air can be brought through 

 the pipette, B.^^ ^he animal is allowed to breathe into this 

 bubble after an equilibrium is practically estabUshed between the 



1" Elsa Kreuger. Ueber die Bedeutung des Elythralraumes bei Dytiscus. 

 Lund Universites Arsskrift. N. F., Bd. 10, No. 13, 1915. Kongl. Fysiografiska 

 Sallskapets Handlingar. N. F., Bd. 25, No. 13. 



11 The air is kept in a hollow metal platelet, which is fixed to the cork by means 

 of screws while the spaces above it were filled up with plasticine. 



^'^ For this reason the cork must not fit too tightly in the beaker so as to 

 allow the water to escape at the rim. 



