THE CRUSTACEANS. 207 
and defenceless, he pays dearly for all the cruelties he mercilessly 
practised in the days of his power. 
The crustaceans do not possess, like the animals higher in the 
scale of life, a vertebral column—that is, a stiff, calcareous axis, 
from which branch out bones of a similar nature, forming the 
skeleton; but they possess a stony covering, which is secreted 
by the tegument which covers them, and thus forms an external 
skeleton. Thus the crustaceans live within their skeleton, and 
their flesh does not, as in the case of the vertebrata, surround the 
bones. Such a skeleton is termed devma/, or tegumentary. 
The armour of the crustaceans is of a sombre hue, here and 
there a dash of blue enlivens their colour, reminding one of the 
steel-blue of the knight’s corslet. Some few are of a reddish tint, 
but the race is devoid of gaudy colouring, in spite of the assertion 
of the poet, who depicted the scarlet lobster crawling over the 
submarine rocks. In the dorsal region the shell is very thick, and 
capable of great resistance; their members are also remarkable for 
their hardness, yet in the smaller species the shell is so thin that 
the processes of circulation and digestion can be seen in opera- 
tion. Many of the crustaceans are quite microscopic, and in such 
numbers that they contribute to the colour of the ocean a purple, 
violet, and even a red tint; such are the Grimothea D Urvillei 
and the Grimothea gregarea. 
In the Sea-spiders, which have no neck, the head is lost in the 
breast (cephalothorax); the belly, however, remains distinct. The 
middle of their body is compressed, and yet the form is not 
ungraceful. Those crustaceans which have no pretence to contour, 
have their head, breast, and belly all in one mass; thus they are 
short and squat, and most difficult to seize. Many of these 
animals have a powerful tail, which consists of a number of 
ciliated plates, arranged as paddles. This member assists the 
crustacean in swimming, and with it it beats the water to confuse 
its enemies. 
As aquatic animals, the crustaceans breathe by dranchie. In 
the larger species these organs are lamellar, or composed of fila- 
ments, their supports being traversed by two blood-vessels, one of 
which directs the fluid to the body, the other to the heart. These 
lung apparatus are usually enclosed in the body, but in some of 
