1 40 E VOL UTION AND BISEA SE. 



legists hold the opinion that all these appendages are 

 modifications of a common type. Normally the eye- 

 stalk corresponds to the protopodite of an abdominal 

 limb, consisting of a short basal and a long cylindrical 

 terminal joint, the distal surface of which is covered with 

 corneal facets. In A. Milne-Edward's Palinurusvtz find 

 a normal ophthalmite on the right side, but the left one 

 " has taken on antenniform characters." 



FIG. 77. Cephalon of a Rock-lobster (Palinuruspcnicillattis), 

 with an antenniform process growing from the inner 

 aspect of the eye-stalk. (After Howes. 1 ) 



Professor Howes points out that the corneal facets 

 on the eye-stalk of decapod crustaceans do not in 

 many instances surmount the whole of the free sur- 

 face ; frequently the outer free border is destitute of 

 corneal facets, and often is swollen and well differen- 

 tiated. This is so in Palinurus, and would serve to 

 support the view that the facetted portion of the oph- 



1 "Proc. Zool. Soc." 1889. 



