SECTION VI 

 THE SENSORY ORGANS 



IN our endeavour to deduce the sensory organs of 

 Apus from those of a carnivorous Annelid, we must 

 not forget that the development of an exoskeleton 

 must necessarily lead to striking modifications. 

 Such modifications, important in all the organs, are 

 especially so in those which, like the sensory organs, 

 lie at the surface in more or less immediate contact 

 with the outer world. We will take the sensory 

 organs in turn, and discuss the changes which took 

 place in them during the transformation of the 

 Annelid into the Crustacean. 



The antenna, as sensory organs, admit without 

 difficulty of deduction from the antennae and antennal 

 parapodia of the first two segments of the Annelid, 

 as we have already seen in the section on the 

 appendages. 



The round white spot behind the eyes of Apus 

 has often been taken to be a sensory organ, and we 



