288 ON THE OLFACTORY SEl\ffi OF THE CLADOCERA. 



Fig. 7. An olfactory setae from Asellus aquaticus x 1,000. 

 Given for comparison, a. Hyaline distal por- 

 tion of seta divided into two sections by a 

 slight difference in diameter, b. Stalk with 

 strongly chitinised walls. o. Epidermis of 

 antennule. n. Nerve thread to ganglion. 

 „ 8. Antennule of Alona a finis x 275. 

 „ 9. ,, ,, Alona qnadrangularis X 275. 



„ 10. ,, ,, Bythotrephes longimanus. Example 



of an antennule with 5 olfactory 

 seta?, a. Accessory simple seta. 

 „ 11. „ „ Holopediu-m gibberum x 450. Ex- 



ample of an antennule with 6 

 olfactory setae. a. Accessory 

 simple seta. 

 ,, 12. „ ,, Leptodora hyalina X 120. Example 



of an antennule with 9 olfactory 

 setae, a. Accessory simple seta. 



