134 i I;!;DI:I;I< K TILXKY AND LUTHER F. AVARRKN 



])'\ih n nces observed in the </>//>h//xil cn//i/>I<:c in ///< 



species of r<-/>i.il<* <ilri</// ///rc^i./i/aicd. 

 PROSAURIANS 



1. S/>li< //<><l/i imiicialiuH (Htttterift). Spencer ('86) ; 367 Leydig 

 '91) ; 23 Hoffmann ('90) ; 187 Dendy C99) 87 described a develop- 

 ment, as did also Schauinsland 346 in 1899 and 1903. 



The pineal organ in the embryo is a simple evaluation \vitli a 

 thin stalk which is solid. The walls of the end-vesicle have 

 ]n;iiiy folds. Only the cells in the interior retain a brown pig- 

 ment. The parietal nerve, according to Spencer, is a prolonga- 

 tion from the end of the epiphysis. Such a connection does 

 exist in some adults, but is of a connective tissue character. 

 Dendy and Schauinsland identified the actual parietal nerve. 

 It arises in front of the epiphysis and is independent of it. The 

 parietal eye is conical or pyriform in shape and the retina and 

 lens are both well developed. In olden 1 embryos the nerve 

 does not enter the middle, but rather comes into relation with 

 the posterior third of the eye. The structure of the retina 

 was most minutely described by Spencer, Leydig, and Dendy. 

 It has rod cells and several other layers of cells. It contains 

 pigment as well as a molecular layer and a layer of large gan- 

 glionic cells. The lens is bi-convex. The entire organ is sur- 

 rounded by a connective tissue capsule. Dendy mentions a 

 thin-walled sac in the embryo between the epiphysis and para- 

 physis. This undoubtedly is an accessory organ. $i)li>'ti<nlon 

 has a parietal foramen and a superficial apparatus usually con- 

 nected with the parietal eye. 



SAIIMAXS LACERTILIA VKKA. 



< ii:< KOXIDAE. 1. Gecko verus. Spencer ('86). 3 " In this spe- 

 cies only the epiphysis is present. Then 1 is no parietal foramen 

 and no parietal spot. 



2. /'luii/thirti/lii* muralis. Spencer ('86) ; 3 ' 17 Leydig ('91) ; 238 

 Melrhers ( '99 ).--''''' In this form there is no parietal eye, the 

 epiphysis being the only element to appear. This latter con- 

 sists of an end-vesicle which is large and thick-walled having 

 no folds; its stalk is short and solid. The entire pineal organ is 



