24



Dr. E. Hopkinson,



dimensions attain half the thickness of a lead-pencil. It is these

that prepare the respiratory functions of the embryo and assist

exchanges with the external air. The air-chamber increases during

the last hours of embryonic life ; it alone is transparent, all the rest

is opaque, but the movements of the embryo are visible.


Hatching.


The vitellus and the yellow fluid contained in the two pouches

return into the interior of the abdomen ; the vitellus constitutes a

food reserve which allows the chick to live from eight to ten or even

fifteen days without taking any other nourishment.


This absorption of the vitellus and fluid takes place several

hours before hatching. The fluid soaks into the subcutaneous tissue

and swells up the neck and feet, markedly increasing the size of the

body; the skin is no longer wrinkled, but regularly distended. The

chick is ready when the vitellus is deprived of its blood-supply, when

the body occupies the entire shell. But it is necessary in order to be

free for it to attack the fibrous, highly resistant membrane which

lines the shell. The chick uses its saliva: around the beak the

membrane becomes actually macerated, losing all its tenacity; the

blows which the little thing instinctively delivers end in the egg-shell

itself being attacked. Exceptionally, in artificial incubation, the

chick liberates itself; if this occurs, it is a sign of strength. In

other cases it rests with the operator to complete the hatching.



THE PIGEONS OF THE GAMBIA,


By E. Hopkinson, M.A., M.B., D.S.O.


The Green Pigeon (Vinago calva).


Columba calva. Temm. and Knip (Pig., i, 1811, p. 35, pi. vii; coasts

of Loango and Angola).


Vinago nudirostris. Swainson (Birds of Africa, vol. ii, p. 205; Sene¬

gal, cf. p. 203; Brit. Mus. Hand List).


Range: Senegambia ; North-east and East Africa. (Brit. Mus. Hand

List.)



