560 



Mr. W. B. Spencer. 



[June 10, 



favourable position immediately beneath the epiblast, and, he states, 

 there is no difficulty in the way of the idea that an unpaired sense 

 organ similar to the eye would be developed out of the pineal gland. 



Ahlborn* also, in 1882, independently arrived at the conclusion 

 that the epiphysis is to be regarded as the remains of an unpaired 

 median eye, founding this conclusion upon general considerations, 

 such as the agreement in origin of the eye vesicles and the epiphysis 

 as hollow outgrowths of the brain, the connexion of the epiphysis 

 with the eye region of the brain (especially the optic thalami), and 

 the peripherally directed position of the structure in Selachian Ganoids 

 and Petromyzon, and the completely peripheral position in Amphibia 

 on the outside of the skull. He even goes so far as to suggest a 

 comparison of this structure with the unpaired eye of Amphioxus and 

 Tunicates. 



More lately Henri de Graaff has published an outline of his 

 results in studying the development of the epiphysis in Amphibia, and 

 its structure in the adult Lacerta agilis and Anguis fragilis. 



He agrees with Strahl and Hoffmann in stating that the "frontal 

 organ " of Leydig is the distal part of the epiphysis completely sepa- 

 rated off from the proximal. 



He describes in detail the structure of the organ in Anguis, where 

 it develops, he says, into a structure very similar to a highly 

 organised invertebrate eye, as that of Cephalopods, Pteropods, and 

 Heteropods. 



The following is a preliminary notice of results obtained recently 

 by studying the structure of the organ in various forms of lizards, at 

 the suggestion of Prof. Moseley, and by means of materials procured 

 for the purpose with great kindness by him from various sources. J 



The forms investigated at present are the following, though only 

 the more important results obtained from a few are given in this 

 abstract : — 



Hatteria punctata. 

 Lacerta ocellata. 

 Lacerta vivipara. 

 Iguana (2 sp.). 

 Galotes ophiomaca. 

 Galotes versicola. 

 Leiodera nitida. 

 Plica umbra. 



Anolius (sp ?). 

 Grammaiopleora barbata. 

 Chameleo vulgaris. 

 Stellio cordylina. 

 Varanus bengalensis. 

 Varanus giganteus. 

 Cyclodus gigas (?). 

 Seps chalcidicd. 



* " Ueber die Bedeutung der Zirbeldriise." "Zeit. fiir Wiss. Zool.," vol. 40 

 (1884), p. 336. 



f "Zur Anat. u. Entwick. der Epiphyse bei Amphibien u. Keptilien." Zool. 

 Anzeig., Jabrg. 9 (1886), p. 191. 



X I am especially indebted to Professor Gunter, through whose kindness I have 



