222 Dr John Davy's Observations on the 



The observations of M. Vogt were made principally on 

 the ova of the Palee (Coregonus Palcea, Cuv.) of the Lake of 

 Neuchatel. Those which I have to offer, have been made in 

 most part on the mature ova of the Charr of Windermere. 

 These, it may be right to mention, are commonly spherical, 

 about two-tenths of an inch in diameter, weighing about a 

 grain each (the fluid contents about *98 of a grain ; the mem- 

 branous shell about *02 of a grain), of the specific gravity 

 1095, or thereabouts, — being suspended in a solution of com- 

 mon salt of this density. The contained fluid — the vitellus — 

 is slightly viscid ; of a light yellow hue, from oil particles of 

 this colour diffused through it ; and slightly alkaline, as in- 

 dicated by its effects on test papers. 



Having premised thus much, I shall briefly relate the re- 

 sults of the experiments which I have made ; and, first, On 

 the action of water on the vitelline fluid. 



When about equal parts of the fluid of the egg and water 

 were mixed, the result was an immediate coagulation, exactly 

 similar to that described by M. Vogt in the instance of the 

 vitellus of the Palee. If the proportion of water was very much 

 less, the two fluids mixed without coagulation, either at the 

 instant or afterwards. The mixture was capable even of dis- 

 solving a minute quantity of coagulum obtained by the action 

 of a larger quantity of water. When a puncture was made in 

 the egg under water, the little fluid that issued was instantly 

 covered with a delicate pellicle, and was shortly wholly 

 coagulated, as were also, gradually and pretty rapidly, the en- 

 tire contents. 



Secondly, Of the action of heat. — Contrary to what might 

 have been expected, heat, even a temperature of 212° 

 Fahrenheit, did not coagulate the vitellus. Eggs placed 

 in a dry tube immersed in boiling water, shrunk and became 

 shrivelled from evaporation, but not opaque ; and when 

 evaporation was arrested by the presence of steam, gene- 

 rated from accompanying moist cotton, even this change 

 was prevented ; after immersion of the tube from five to 

 ten minutes in boiling water, the vitellus remained fluid, 

 coagulable, however, as before, on admixture with water. 

 Heated in water, the effect was strikingly different. At 160° 



