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of the discovery of the pineal eye is usually accorded to de Graaf 

 because he first showed that in Anguis it is actually eye-like in 

 structure. 



Very soon after the appearance of de Graaf's article, Spencer 

 published, in October, 1886, an elaborate memoir "On the Presence 

 and Structure of the Pineal Eye in Lacertilia", showing the structure 

 of the organ in a large number of types. This work, with that of 

 de Graaf, gave a substantial basis of fact to the theoretical con- 

 clusion of Rabl-Piückhard and Ahlborn, viz., that the distal capsule 

 of the epiphysis is a rudimentary unpaired eye in vertebrates. 



Since the work of de Graaf and Spencer, the pineal eye has 

 been made the subject of investigation by most competent morpho- 

 logists. Beraneck, Beard, Francotte, Owsjannikow , Hoffmann, 

 Strahl and Martin, Selenka, Leydig, have all contributed to our 

 knowledge of that interesting sense-organ and, through their rese- 

 arches, much has been made known regarding its structure in lower 

 Vertebrates. 



One result of the closer study of the brain region from whence 

 it springs, has been, to show that the roof of the thalamencephalon is 

 the seat of at least two, and, possibly three, outgrowths (epiphysis, 

 pineal eye and paraphysis). 



Notwithstanding all the researches upon the pineal eye we are 

 still very much in the dark regarding its derivation. Although several 

 researches have been undertaken with the expressed purpose of deter- 

 mining its origin, very little has been accomplished in that direction, 

 and nothing more significant has been brought to light than, the point 

 of common agreement, that the epiphysial outgrowths arise (after 

 the brain is well advanced in development) as outgrowths from the 

 roof of the thalamencephalon. No traces of the earlier development 

 of the pineal organ have been found, and its time of origin has been 

 supposed to be the moment when it first appears in the median plane. 



Beard, in his paper on the parietal eye in Cyclestomes, expresses 

 himself as follows : "It was with the hope of getting at the phylogeny 

 of this remarkable sense organ that I began researches upon its 

 development and its distribution in the group of Fishes. But indeed 

 the result was to find that the development explains very little" etc. 



But the development, when it is known, is likely to explain a 

 great deal, and very much is still to be expected from a systematic 

 search for the early development of this organ in the group of Cyclo- 

 stomes and other fishes. 



I have been fortunate enough to trace the principal epiphysial 



