399 THE WORLD OF THE SEA. 
filaments, and is really the germ which contains all the organs of 
the young bird in an undeveloped state. At one point of its circum- 
ference a white spot appears. This gradually expands until about 
a quarter of the yellow ball is white ; this may be distinctly seen 
to be divided into two parts. The upper layer soon begins to 
give signs of organisation—a red vein runs round its edge, from 
which numerous branching vessels are given off, and tend towards, 
not a point in the centre, but a long, dark line, which is surrounded 
by a white border. All the veins collect into four main branches, 
which enter this lineal opening in pairs, one on each side. As the 
wonderful process goes on, the outline of the brain and heart appears, 
from which organs the blood-vessels take their rise. The respira- 
tion had hitherto been conducted by the vascular net-work of the 
yolk, but now a temporary lung is established, and the development 
proceeds rapidly ; the contour of limbs begins to be traced, and the 
eye is defined at an early period. The scales of the legs and the 
germs of the feathers are very visible. The air-chamber, with 
which all are familiar, which is situated at the thick end of the egg, 
has gradually increased, so that when the young bird is fledged, 
and ready to make its début, it occupies almost one-quarter of the 
whole egg. This is a wise provision in order that the little prisoner 
may have room to move in the shell when its instinct prompts it to 
break the walls. The bird, at the right moment, tears the mem- 
brane of the air-chamber, and enters this open space. Now more 
at ease in its prison, it attacks the shell, striking it with a little 
hard substance, fitted at the extremity of the beak, the prison 
walls are broken, and the captive emerges into the external world. 
Sea-birds defend their eggs and their little ones very bravely. 
When Captain Ross discovered the Island of Possession, he found 
there an immense quantity of penguins, covering even the tops of 
the hills. These birds advanced towards the shore in close columns, 
and with their beaks bravely attacked the Englishmen who wished 
to take possession of the land in the name of Victoria! All honour 
to the courage and patriotism of the penguins! 
The female of the wild duck, when going to her nest, alights a 
hundred paces or more away from it. When on land she moves 
towards her nest obliquely and tortuously, with her eye fixed on 
