730 STRUCTURE OF THE DORSAL PAPILLA OF ONCHIDIUM. 



PRELIMINARY REPORT ON THE HISTOLOGICAL 

 STRUCTURE OF THE DORSAL PAPILLA OF 

 CERTAIN SPECIES OF ONCHIDIUM. 



By R. von Lendenfeld, Pn.D. 



(From the Australian Museum Laboratory.) 



The structure of the tubercles was studyed by means of section 

 series, through specimens of Onchidium chameleon, Brazier, 

 described above, and Onchidium Diimelii, Semper. The specimens 

 were collected by Mr. Whitelegge in Port Jackson, hardened with 

 osmic acid and stained in various ways. 



The results of this investigation are the following : — 



1. Onchidium chameleon has small papillae and has no eyes, 0. 

 Damelii has generally three large eyes on each papilla, these are 

 situated laterally. 



2. My investigations carried on with excellent material, corro- 

 borate the descriptions given by Semper (1) of the eyes of Onchidia 

 perfectly. 



3. The eyes of Onchidium Damelii belong to Semper's group I., 

 eyes with an epithelial retina. 



4. The epithelium of the tubercles is of identical structure in 

 the species with, and the species without, dorsal eyes, and formed 



(1) C. Semper. Ueber Sehorgane von dem Typus der Wirbelthieraugen 

 auf dem Riicken von Schnecken — Reisen ini Archipel der Philippinen 

 Zweiter Theil. 



