PARTS OF ANIMALS, II. viii. 



Tortoises, are apparently in like case. On the other 

 hand, the Insects and the Cephalopods are differ- 

 ently constructed from these, as well as beino• 

 different from each other. Not only, as it appears, 

 have they no bony part, but they have practically 

 no earthy part at all distinct from the rest of the 

 body. The Cephalopods are almost wholly soft 

 and fleshy, yet in order to prevent their bodies 

 from being easily destructible as fleshy struc- 

 tures are, the substance of Avhich they are formed 

 is intermediate between flesh and sinew, having the 

 softness of flesh and the elasticity of sinew. When 

 it is split up, it breaks as flesh does, that is, not 

 longitudinally but into circular portions. The reason 

 for this seems to be that such a structure secures 

 the greatest strength. There is found also in these 

 creatures the counterpart of the spinous bones of 

 fishes ; examples are : the " pounce " (o$ sepiae) of 

 the cuttlefish, and the " pen " (gladius) of the 

 calamaries. Nothing of this sort, however, appears 

 in the Octopuses : this is because in them what is 

 called the " head " forms but a small sac, whereas 

 in the cuttlefish and calamaries the " head " is of 

 considerable length. So we see that, in order to 

 secure that they should be straight and inflexible, 

 nature prescribed for them this hard support, just 

 as she gave to the blooded creatures bones or spines. 

 Quite a different contrivance obtains in the Insects — ■ 

 different both from the Cephalopods and from the 

 blooded creatures, as has already been stated. In 

 the Insects we do not find the clear-cut distinction 

 of hard parts and soft ; here, the whole body is hard, 

 yet its hardness is such that it is more fleshlike than 



161 



