SPIDERS. 723 



The tail is, as may be supposed, the great aid to locomotion in the 

 lobster family, and they can swim backwards with great rapidity by its 

 assistance. Lobsters shed their claws when alarmed, and are easily caught 

 by a glittering bait. 



The hermit crabs are interesting creatures, but do not possess the horny 

 coat of the crab or lobster. They are therefore compelled to inhabit an 

 empty shell, into which they thrust themselves, holding to the bottom of it 

 by their tail, while a large claw guards the entrance. When the animal gets 

 too big for his house he moves to another, leaving the old home for another 

 hermit of the shore. 



The crabs have no developed tails, and are therefore called brachyura 

 " short-tailed," and they are walking creatures. There are king crabs, land 

 crabs, and the common swimming crab. These animals can shed their 

 shells as other crustaceans, and a curious fact is they shed them whole. 

 How the claws come out must remain more or less a mystery. Reaumur 

 investigated the action of the crayfish, and noticed that as the casting time 

 approached the Crustacea retired to some hiding-place and remained without 

 eating. The shell becomes gradually loosened, and at last by putting its 

 feet against a stone and pushing backwards the animal jerks himself away. 

 It must be a painful operation, for the mill-like teeth of the stomach are 

 also rejected, and the joints do not give way. After a while a new shell 

 appears, and is cast in due time as before. 



The eyes of the Crustacea are situated in front, and are composed like 

 the insects, or are simple, like spiders. They possess a sense of hearing evi- 

 dently. The eggs of the lobster are carried by the female, and they are 

 termed the " coral " in consequence of their red and beadlike appearance. 

 Our space will not admit of our saying much more concerning the interest- 

 ing Crustacea, though the barnacles, so well known by sight by all dwellers 

 at the sea, and called Cirripedia, which fix themselves to rocks and ships, 

 deserve notice. The young are capable of movement, and this fact was first 

 discovered in 1830. It resembled a mussel, but when kept in sea-water it 

 adhered to the vessel which retained it. The cirripedia are so called from 

 the cirri or arms which they possess, and by which they are enabled to 

 entangle or catch their food, as in a net. They hold themselves by a 

 " foot stalk." The goose-mussel, or barnacle, is very common, but must not 

 be confounded with the limpet. 



Dr. Baird gives the following description of them : " The cirripeds 

 are articulated animals contained within a hard covering composed of several 

 pieces and consisting of calcified chitine. The body of the animal is 

 enclosed in a sac lined with the most delicate membrane of chitine, which 

 in one group is prolonged into a peduncle and contains the ova ; the body 

 is distinctly articulated and placed with the back downwards, 



ARACHNIDA SPIDERS. 

 There are many families of arachnida besides tne well-known garden 



