Sense-organs 49 



eyes, whicli are never replaced, but persist as the eyes 

 of the fly. If this is really the case, the number of 

 elements must be greatly increased during transforma- 

 tion. Weismann believes that the imaginal eye of 

 Corethra,. though not superficial, is functional in the 

 transparent larva '. 



The antennae consist of a basal piece, relatively large, 

 which carries two terminal pieces of nearly equal length, 

 one jointed and one simple, the former consisting of four 

 joints ; a stout seta projects from the basal joint. There 

 is a circular sensory spot about the middle of the basal 

 joint; a similar spot occurs on the maxillary palp of 

 the Phalacrocera-larva. 



It seems probable that the antennae of the Chironomus- 

 larva are of limited physiological importance ; they are 

 minute and of comparatively simple structure. 



On the dorsal surface of the last segment, and at the 

 very end of the body, are a pair of sensory appendages. 

 Each bears several long setae, and is in close connexion 

 with a ganglion at its base. The ganglion is no doubt 

 connected with the abdominal nerve-cord, but we have 

 not made out the connexion to our satisfaction (see p. 45). 

 In the Tanypus-larva these prominences are long, and 

 the setae numerous (see p. 33). 



4. Alimentary Canal. 



The alimentary canal of the larva takes a nearly General 

 straight course through the body, which it slightly tion. 

 exceeds in length (fig. 40). It is subdivided into oeso- 

 phagus, stomach, and intestine. The stomach includes 

 a distinct anterior region, which we shall call the cardia 

 or cardiac chamber, while the intestine is divisible into 

 a small intestine in front, and a large intestine or colon 



' Weismann, 1866, p. 16. 



UIALL. E 



