92 E. NEWTON HARVEY. 



gas. I believe the addition of platinized asbestos to the fluid 

 through which hydrogen is passed will prove of great value to 

 biologists in the study of cells under anaerobic conditions. 



Instead of Pt asbestos, colloidal Pt or colloidal Pd may be 

 used. The latter is conveniently prepared by adding to 5 cc. 

 0.2 per cent. PdCl 2 just enough dilute NaOH to make the PdCl 2 

 darken without giving a precipitate of basic PdCl 2 , and then 

 one drop of .042 per cent, hydrazine hydrate. The finely divided 

 Pd adsorbs a good deal of hydrogen and will keep a solution free 

 of oxygen for some time, as can be observed by using as indicator 

 the luminescence of a mixture of luciferin and luciferase. 



In order to show that the luminescence of Ctenophores, like 

 Beroe, is independent of dissolved oxygen, it must be recalled that 

 an extract made by squeezing Beroe through muslin and filtering 

 through filter paper is non-luminescent itself, but gives a brilliant 

 light on addition of fresh water, dilute salt solution, or various 

 cytolytic substances like saponin, sodium glycocholate, ether, 

 etc. Accordingly I tried the experiment of mixing Beroe extract 

 made free of oxygen by Na 2 S 2 O 4 with m/io Na 2 HPO 4 solution, 

 also made free of oxygen by Na 2 S 2 O 4 . The Na 2 HPO 4 was used 

 instead of fresh water in order that the reaction would be alkaline 

 enough to allow rapid coloration of leuco-methylene blue, added 

 as an indicator, should any oxygen leak into the apparatus. 

 This is shown in Fig. i. In A is placed Beroe extract + Na 2 S 2 O4 



FIG. i. 



