554 



E. RAY LANKESTER. 



region of the body ; it becomes tlie palp or jointed process of 

 anterior segments. A second ramus, the '' exopodite/' often is 

 also retained in the form of a palp or feeler. In Apus, as 



,£n^ 



£n3 



En-f 



Fig. 10. — Tlie first thoracic (fourth post-oral) appendage of 

 A pus caiicriformis (riglit side). Ax"^ to A.v^, tlie four seg- 

 ments of the axis with muscular bands ; £"«', gnathobaso ; En'' to En^, 

 the elongated jointed endites (rami); Eii^, tlie rudimentary sixth 

 endite (exopodite of higher Crustacea); Fl, the tlabellum which 

 becomes the epipodite of higher forms ; Br, the bract devoid of 

 muscles and respiratory in function. (After Laukester, 'Q. J. Micr. 

 Sci.,' vol. xxi, 1881.)' 



the figure shows, there are four of these "antenna-like" 

 palps or filaments on the first thoracic linib. A common 

 modification of the chief ramus of the Arthropod parapodium 

 is the chela or nipper formed by the elongation of the pen- 



' Tiiis figure has been re-drawn for the present reprint. — E. R. L. 



