ORGANS OF SMELL IN CRUSTACEA— CENTIPEDES. 49 



eaoh cylinder is a nerve, which apparently swells into 

 a ganglion. 



Leydig described similar organs on the antennae 

 and palpi of various other Crustacea. They have 

 obviously some special function, and he suggests 

 that they are olfactory organs. It is interest- 

 ing that, in certain species which live in subter- 

 ranean waters and have lost their eyes, these olfactory 

 cones are unusually developed. They are much larger, 

 for instance, in Asellus cavaticus and Gammarus 



Fig. 36.— Tip of the antenna of a centipede (Jiilus terrestris\ x 600 (after Leydig). 

 At the apex are four olfactory cylinders, a few of which are also seen on the fol- 

 lowing segment, among the ordinary hairs. 



puteanuSf which live in the dark and are blind, than 

 in Asellus aquaiicus and Gammarus pulex or G.fluviatilis, 

 Fig. 36 represents the end of the antenna of a centi- 

 pede (Julus terrestris). There are four olfactory 

 cylinders at the tip, and several are also seen on the 

 following segment among the ordinary hairs. In this 

 species the cuticle of the cylinder appeared sometimes 

 as if wrinkled, and Leydig believes that the end is 

 open.* Similar cylinders occur in Scolopendra, Glo- 



* Loo. cit, p. 286. 



