IX. OUTSIDE AND IN. 159 



Before ^examining these, remember there are mainly 

 two sorts of joints in the frame work of the 

 bodies of animals. One is that in which the 

 bone is thick at the joints and thin between them, 

 (see the bone of the next chicken leg yon eat), 

 the other is that of animals that have shells or 

 horny coats, in which characteristically the shell 

 is thin at the joints, and thick between them 

 (look at the next lobster's claw you can see, with- 

 out eating). Yon know, also, that though the 

 crustaceous are titled only from their crusts, the 

 name ' insect ' is given to the whole insect tribe, 

 because they are farther jointed almost into 

 scions : it is easily remembered, also, that the 

 projecting joint means strength and elasticity in 

 the creature, and that all its limbs are useful to 

 it, and cannot conveniently be parted with ; and 

 that the incised, sectional, or insectile joint means 

 more or less weakness,* and necklace-like laxity 

 or license in the creature's make ; and an ignoble FIG. '22. 

 power of shaking off its legs or arms on occasion, coupled 

 also with modes of growth involving occasionally quite as- 

 tonishing transformations, and beginnings of new life under 

 new circumstances; so that, until very lately, no mortal 

 knew what a crab was like in its youth, the very existence 



* Not always in muscular power ; but the framework on which 

 strong muscles are to act, as that of an insect's wing, or its jaw, is 

 never insectile. 



