iv. 5. 99 



does so ; and this gives it protection.'^ These then are the 

 reasons why the ink-bag is much larger in the sepia than in 

 the other Cephalopods; and its larger size again explains its 

 lower position. For though this position removes it farther from 

 the funnel, yet the larger size .of the bag gives increased force, 

 and so allows the ink to be ejected wfth ease even from a distance. 

 The ink itself is of an earthy character, in this resembling the 

 white deposit on the surface of a bird's excrement. And the 

 explanation in both cases is the same, namely the absence of an 

 urinary bladder.^'' For, in default of this, it is the ink that serves 

 for the excretion of the earthy matter. And this is more 

 especially the case in the sepia ; because there is a greater 

 proportion of earth in its composition than in that of the other 

 Cephalopods. The earthy character of its bone is a clear proof 

 of this. For in the poulp there is no bone at all, and in the 

 calamary it is small and merely cartilaginous.'^ Why this bone 

 should be present in some Cephalopods, and wanting in others, 

 and how its character varies in those that have it, has now been 

 set forth. 



These animals, having no blood, are in consequence cold and 

 of a timid character.'^ Now, in some animals, fear causes an 

 evacuation from the bowels, and, in. others, a flow of urine from 

 the bladder.20 Similarly in these it produces a discharge of ink, 

 and though this ink, like the urine, is residual matter, and though 

 its ejection in fright is merely the result of necessity, yet it is used 

 by nature for a purpose,^' namely the protection and safety of the 

 animal that excretes it. 



The Crustacea also, both the Caraboid forms and the Crabs,''^ 

 are provided with teeth, namely the two so-called anterior teeth ; 

 and between these they also present the tongue-like piece of flesh, 

 as has indeed been already mentioned.^^ Directly after their 

 mouth comes a gullet, which is very small considering the size of 

 the whole body ; and then a stomach, which in the Carabi and 

 some of the Crabs is furnished with a second set of teeth, the 

 anterior set being insufficient for mastication. From the stomach 

 an unconvoluted gut runs in a direct line to the vent.^* 



The parts described are to be found also in all the various 



Testacea.25 The degree of distinctness, however, with which they 



are formed varies much in the different kinds, and the larger the 



size of the animal the more easily distinguishable are all these parts 



679 b. 



