Dr John Davy on the Eggs of Birds. 257 
The following is a tabular view of the results :— 
3 
g 43 : Sy 4 a= 
a ba} oS leven! oe 3 
= las lwo | Ss as £8 | 3 |Consistence. Colour, &e. 
Bo |(Od(SonIlS en laglen j S 
Star alr sleet 2S 
Pie : a 764°5| 10°13] 25-21] 64°5 | 55-0| 10:19|—160°| Hard. White. 
Pigeon’s . . . |278:0) 8:05| 17-94] 73-95] 39°3/ 11°5 |—189°| Pretty firm. | Bluish. 
Jay’s . . . . |127-3| 5-03] 26-86] 68-11] 30-0] 12°8 |—184°| Soft. es eee 
Missel Thrush’s 124 6] 5°53) 12°84| 81:30) 24 3)10°2 |—188°| Soft. Transparent. 
Starling’s. . . {115° | 7°12) 14:25) 78-62) ... —195°) Firm. White. 
2: 
Robin's . . 4 IE ee ieee ae 82) |_ 19741 soft, White. 
Hedge Sparrow’s | 345] 5:79] 21-45/ 72°46] 58.1] 12-2 |—168°| Pretty firm. { Cee trans- 
Golden-crested : : : : Pl ays Bluish, semi- 
muen-crested } | 14-3| 4-90| 24°05] 43°6 | 43-6) 9:9 | ...... Soft. pet as 
The differences, as shown by these results, are not great. 
So far as they allow of inference, they seem to show—l1. (as 
already remarked), That the smaller the egg, the smaller 
the bird, the shorter the period of incubation, the thinner 
is the shell, and the more elastic and the smaller the pro- 
portion of calcareous incrustation, and in consequence the 
more pervious to the air, essential to life and development ; 
though even as to this there seems to be no exact ratio, and 
there appear to be exceptions.* 
2. That the albumen in quantity greatly exceeds the 
yolk, but in no regular proportion ; whilst the quantity of 
solid matter in the yolk is proportionally much larger per 
cent. than in the albumen. 
3. That the temperature at which coagulation takes place 
varies in almost every instance; and that the firmness of 
the coagulum does not appear to be regulated by the pro- 
portion of solid matter obtained by evaporation. 
4, That the coagulum of each has an aspect of its own, 
varying in the different instances as to kind and degrees of 
translucency. 
Though all the experiments were made with care, I must 
* Probably the size of the egg, the quantity of nutritive matter it contains 
(as suggested in my “ Physiological Researches,” p. 159), bears some relation 
to the condition of the young bird on leaving the egg, and its habits, espe- 
cially as to feeding, ¢.e., whether it has to find its food after the manner of 
the offspring of the Natatores and Rasores, immediately on starting into 
active life, or is provided with food till fully formed and capable of taking 
wing, by the parents, after the manner of the Columba, Passores, and Raptores. 
