PINEAL EYE IN LAOERTILIA. l'79 



and their processes in this region run in many cases [n'^) 

 directly into connection with the fibres of the optic stalk. 

 The layer gradually thins out anteriorly until that part is 

 reached where, in the neighbourhood of the lens, the pigment 

 is present through the whole breadth of the wall. In its 

 thickest part the whole layer (consisting of the double or triple 

 row of elements) is about the same breadth as the layer of 

 rods. 



(3) External to the spherical elements lies a thin layer con- 

 sisting of a fine punctated material, which takes the stain 

 (hsematoxylin) with difficulty but contains numerous scattered 

 fine pigment granules. Into this, which may be called the 

 Molecular layer,^ pass processes from the retinal elements 

 on either side (fig. 2, mo.). The layer in question is a very 

 thin one in Hatteria punctata, but forms, when seen in 

 section (fig. 2), a definite boundary line separating the retinal 

 elements into an internal and an external division. Poste- 

 riorly the layer spreads out and surrounds the specially 

 elongated rods in the optic axis, anteriorly it reaches as far 

 forwards as the ring of pigment surrounding the lens. It is 

 possible that this layer and many of the processes passing into 

 it may be of the nature of supporting structures. 



(4) A layer of nucleated spherical elements (fig. 3, n") lying <u^/>'^ ^ 

 close to the molecular layer, and distinguished from those on 



the inner side by their greater size; they are arranged so as to 

 alternate (the alternate arrangement is, however, by no means 

 perfectly constant) with 



(5) A layer of cone-shaped bodies {Co.) in which no nuclei 

 can be detected. They lie with their broad ends externally, 

 and gradually taper internally till their pointed ends are 

 closely in contact with the molecular layer into which pro- 

 cessses from them run (fig. 3). 



(6) Between the bases of the above are a series of spindle- 

 shaped elements with nuclei, from which processes pass off 

 internally, which may either run directly into the molecular 

 layer or into the spherical bodies on its external side. At the 



' Cf. de Graaf, PI. 4, fig. U, gl. 



