320 RUPERT VALLENTIN AND J. T. CUNNINGHAM. 



of these " eyes/' Claus poiuts out that they had previously 

 been seen by Dana 1 and Semper, 2 the latter of whom judged 

 them to be eyes, and by Kroyer, 3 who found them in a form 

 which he named Thysanopoda inermis, and thought they 

 were probably auditory organs. The species in which Claus 

 examined the organs was one occurring abundantly at Messina; 

 he named it Euphausia Miilleri. He states that the organs 

 were present on the basal joint of the second and seventh pair 

 of thoracic appendages, and between the two members of each 

 of the four anterior pairs of abdominal swimming feet, so that 

 they were eight in number, two pairs and four median. They 

 were reddish, pigmented, cylindrical bodies, whose immediate 

 relation to the ganglia of the nerve-cord testified to their 

 importance as sense organs. Although Claus did not succeed, 

 notwithstanding earnest and repeated endeavours, in tracing 

 out the nerve-endings, he concluded from the whole structure, 

 and from the presence of lenses and muscles which rolled the 

 organs to and fro, that in all probability they were movable 

 organs of vision. The structure of all the organs was similar. 

 Each bulb lay in a hemispherical protuberance of the body 

 covering, fastened by slender threads, and movable by several 

 oblique muscle-strands. The external wall of the bulb was 

 formed by a cuticular envelope to which the threads and 

 muscles were fastened, while the internal parts were more 

 complicated. The front part of the contents consisted of a 

 transparent kind of vitreous body, bounded behind by a 

 glistening ring containing a lens. Behind the lens, followed in 

 the centre of the " eye," a likewise highly refractive striated 

 body composed of a number of closely packed rods. This 

 body was enveloped in a clear spherical layer, whose posterior 

 half fitted into a course pigmented fibrous membrane. This 

 latter was in immediate contact with the wall of the bulb, and 

 had the form of a hemispherical pigmented cup, open in front ; 



1 'Expl. Exped. of the United States,' " Crust. I," p. 639. 



2 " Reisebericht," ' Zeit. f. wiss. Zool.,' Bd. xii, 1862. 



3 " Forsog til en monog. Fremst. af slaegt. Sergestes," ' Kon. Dansk. Vid. 

 Selsk. Skrifter,' p. 294, 1859. 



