402 EYCLESHVMER. [Vol. X. 



(•85) have both expressed such views concerning the develop- 

 ment of the paired eyes. 



The fact that Beraneck, Strahl and Martin, Fran9otte, Pre- 

 nant, and others have found a transitory nerve passing to the 

 pineal organ, might even be considered additional evidence of 

 its having been a supplementary organ. Why it should have 

 continued functional in some forms as indicated by a rich nerve 

 supply, and in others degenerated, is an entirely secondary 

 question. 



The origin of the pineal organ, in the manner described by 

 Leydig and Hill may indicate that it is derived from paired 

 sensory areas. The accessory vesicles described by Locy are 

 also very suggestive, and later investigation may prove that the 

 parietal eye arises from the coalescence of two such structures. 

 The recent work of Kupffer, however, on the origin of the 

 secondary vesicle in Petromyzon, in which form the structure 

 is functional, if we may judge from the rich nerve supply, 

 shows nothing which can be interpreted as indicating a paired 

 origin. 



