68 
BIRD-LIFE. 
underneath, and the lower in the tube leading to the 
cavity in the yolk’s centre. On the edge of the centre 
leaf a few minute blood-vessels are to be detected by the 
aid of a powerful microscope, and the tube, forming the 
duct for the spinal marrow, has become bent. All these 
structures, resulting from the first day’s incubation, bear 
no resemblance whatever to the bird into which they will 
become ultimately developed. 
On the second day the genesis of creation proceeds 
with extraordinary rapidity; the spinal tube closes more 
completely; the embryo vertebrae increase in number; 
the bladder-like protuberance at the superior extremity of 
the spinal tube emerges more distinctly, and shows itself 
to be formed of four small hillocks. The foremost pair of 
these receive the addition of another protuberance on 
either side, which appears in the form of a small bladder, 
and a little later, somewhat further back, two more 
similar structures appear: these form the germs of the 
ears and eyes. The formation of the breast and stomach 
is also commenced, inasmuch as the upper layer of the 
germ-spot, by its extension, forms a bag, which latter 
encloses the whole of the yolk. These upper laminae sepa¬ 
rate at a short distance from the middle, and thus allow a 
small sac-like space to arise, from which spring, almost 
immediately, two tubes. These meet the vascular net¬ 
work, which has been formed in the meantime, and unite 
with it, thus forming the groundwork of the heart and its 
two principal entrances. As soon as the blood corpuscules, 
engendered in the separate cells, enter into these 
passages, the circulation of the blood is effected, and our 
little creature now possesses a head and a heart. The 
continuous structure and developement of the separate 
parts proceed on all sides alike, with the greatest 
