188 THE PATH OF DEGENERATIVE EVOLUTION 



a rudimentary eye which has neither pigment nor 

 cornea and is coloured like the general surface of 

 the body. 



Eryonicus (fig. 63) belongs to the same group, 

 and comes from the region of Saint-Thomas in the 

 Antilles, where it lives at a depth of about 825 

 yards. This animal has a reduced optic stalk, 

 but at the extremity of this, where in littoral 



forms the eye 

 is borne, there 

 is only a de- 

 pression as if 

 the eye had 

 been carefully 

 scooped out. 



Willemcesia 

 (fig. 64), a re- 

 lative of the 

 marine cray- 



orirl fln in- 



FIG. 63. Eryonicus coecus. Bate? (After W. Faxon, 

 The Stalk-eyed Crustacea, Mem. of Mus. of Comp., 

 Zool. Harvard College, vol. xviii., 1895.) habitant of the 



Atlantic at a depth of about 3500 yards, is com- 

 pletely devoid of eyes in the adult condition, 

 although it possesses them in the larval stage. 



Scolophthalmus (fig. 65), which lives down to 

 4000 yards, is quite devoid of eyes, but possesses 

 eye-stalks which terminate in spines. 



It seems, then, that different species of deep-sea 

 Crustacea may present different degrees of degenera- 

 tion of the eye. One species in itself exhibits all 



