586 PROFESSOE MARCUS HARTOG. 



derm is then transferred to a watch-glass of clean salt solution 

 for a second wasli, and then to a test-tube with salt solution to 

 which a trace of thymol or chloroform is added. The super- 

 natant liquid is always cloudy, probably from the separation 

 of yolk granules still adherent to the blastoderm, or from their 

 escape from tliu inside of the blastoderm-cells after their death. 

 The behaviour of the liquid, with or without obvious frag- 

 ments of blastoderm, is the same as that with crushed frogs' 

 eggs. When acidulated it has visible little action on added 

 fibrin, but contains enough proteid suspended to show after 

 incubation a good biuret reaction. This is especially well 

 marked when I add more proteid in powder, e.g. a little yolk 

 of hard-boiled egg, treated with alcohol and benzol to remove 

 the oily yellow matters, so as to leave a powder which is 

 nearly white, with no more colour than the dried white would 

 show. After keeping the material in the dark for six weeks, 

 acidulating and adding dried yolk, I only get the faintest of 

 biuret reaction after incubating for twenty hours. This demon- 

 strates the very fugacious nature of the ferment. Guignard 

 noticed that cells of plants which presumably were rich in 

 ferments, as inferred from other reasons, gave a specially 

 deep colouration with Millon's reagent. I find in accordance 

 with this that the extra-vascular blastoderm, carefully washed, 

 is much more deeply stained with Millon than the embryo 

 proper. 



There are some peculiarities about the behaviour of the 

 solutions of hen's egg under the biuret test that require a 

 chemist's attention. In some cases I got a dirty feculent 

 precipitate which materially interfered with the ready recog- 

 nition of the pink colouration. In others, where the solution 

 after the precipitation of the acid albumen still appeared milky, 

 a yellowish scum, like that of white-of-egg dilute solution, 

 save for colour, floated up, and only settled partially and with 

 extreme slowness. In one or two cases in a preliminary set 

 of experiments, of which I omitted to take notes, I got a 

 reddish turbidity on heating, presumably of cuprous oxide; 

 in these cases it occurred that the pink colouration appeared 



