48 



LEY DIG'S OLFACTOEY CONES. 



poda, from one of my memoirs in that group,* and 

 shows the curious clasping organ. 



Leydig, in his beautiful work on the Daphnidse, and 

 more fully ia a special memoir on the subject,t de- 

 scribed certain organs which had been also mentioned 

 by La Vallette. I give below his figure of the 

 terminal segments of one of the smaller antennae of 

 the water-woodlouse (Asellus aquaticus) magnified 500 



times. It will be seen 

 that there are three 

 kinds of appendages — 1. 

 Ordinary stiff, cylindrical, 

 tapering, pointed hairs, 

 which are not connected 

 w ith any nerve. 2. Pale, 

 cylindrical hairs, with a 

 blunt terminatioa and a 

 tuft of fine setae. These 

 •hairs are connected with a 

 nerve, and Leydigregards 

 them as organs of touch. 

 3. Peculiar cylinders, of 

 which there is one to each 

 segment. They are com- 

 posed of three parts, 

 the middle one somewhat 

 wider than the others. The lower third is strongly chiti- 

 nized, like the ordinary hairs ; the other two are more 

 delicate. At the free end he observed, in some cases, 

 a group of very fine, short hairs. At the base of 



Fig. 35. — Terminal segments of one of the 

 smaller antrnnaj of the water-woodlouse 

 (Asellus aquatictts)y x 500 (after Leydig). 

 a, Ordinary hairs (not connected with a 

 nerve); b, sensitive hairs (with a nerve at 

 the base) ; c, special cylinders (olfactory 

 cylinders). 



* Ann. and Mag. nf Natural Hlslory, 1853. 



t " Uebor Geruohs unj Geliororgane dtr Krcbso und Insekten," 

 Mailer's Ar., 1860. 



