io6 iv. 5. 



responding position, but is less easily made out.®"' It should, 

 however, always be looked for in the following situations. In such 

 Testacea as are stationary, between the gullet and the channel 

 through which either the excrement or the spermatic fluid ^ is 

 voided ; but, in those species which are capable of locomotion, 

 invariably in the centre, midway that is between the right and 

 left sides. 



In Insects this important organ lies, as was stated in the first 

 treatise,®^ between the head and the cavity which contains the 

 stomach. In most of them it consists of a single part ; but in 

 •others, for instance in such as have long bodies and resemble the 

 Juli,™ it is made up of several parts, so that such insects continue 

 to live after they have been cut into pieces.'''^ For the aim of 

 nature is to give each animal only one such governing part ; and 

 when she is unable to carry out this intention she causes the parts, 

 though potentially many, to work together actually as one.''^ The 

 phenomenon referred to is much more clearly marked in some 

 insects than in others. 



The parts concerned in nutrition are not alike in all insects, 

 but show a considerable diversity. Thus some have what is called 

 a piercer in their mouths, which is a kind of compound instrument 

 that combines in itself the character of a tongue and of lips.'''' 

 In others, that have not got this anterior piercer, there is an 

 organ inside the mouth that answers the same sensory purposes. 

 After the mouth comes the intestine, which is never wanting in 

 any insect. This runs in a straight line and without further com- 

 plication to the vent ; occasionally, however, it has a spiral coil. 

 There are, moreover, some insects in which a stomach succeeds 

 to the mouth, and is itself succeeded by a convoluted intestine.'''* 

 By this arrangement the larger and more voracious insects are 

 enabled to take in a more abundant supply of food.''''^ More 

 curious than any are the Cicadae. For here the mouth and the 

 tongue are united so as to form a single part, through which, as 

 through a root, the fluids on which the creature lives are sucked 

 up.''^ Insects are always small eaters, not so much because of 

 their diminutive size as because of their cold temperament. For 

 it is heat which requires sustenance; just as it is heat which 

 speedily concocts it,"''^ But cold neither requires sustenance nor 

 concocts it. In no insects is this more evident than in these 

 Cicadae. For they find enough to live on in the moisture which 

 682 a. 



