284 ANDREWS. [Vol. V. 



yet bearing at one end what from surface views appears as 

 a single ellipsoidal, highly refracting body, very slightly pro- 

 truding above the general level of the cuticle. This body is 

 free from pigment for about 30 /jl., and then is buried in the 

 pigment mass : in most eyes it lies at the end towards the 

 base of the branchia, but in oblique eyes it faces towards 

 the inner or outer side, never towards the top of the branchia. 



There is thus but a single refracting body for each eye. 



Besides the pigment of the eyes similar pigment is scattered 

 in a few epidermal cells separate, or aggregated in small patches 

 at places, and then resembling eyes. Moreover, there are trans- 

 verse bands due to the presence of pigment in certain sets of 

 branchial filaments. 



Sections show the relation of the single refracting body and 

 the pigment cells of the eye to be as follows : The refracting 

 body projects inwards obliquely, and is surrounded beneath the 

 cuticle by epidermal cells bearing pigment in their outer ends 

 where adjacent to the side surfaces of this refracting ingrowth ; 

 hence the appearances shown in a transverse section such as 

 Fig. 23, while a section parallel to the long axis of this ingrowth 

 (Fig. 24) shows also a peculiar pigmented cell applied to the 

 abruptly truncated end of this ingrowth, and containing a 

 spherical, highly refracting, and very faintly granular body that 

 does not stain with hematoxylin. The pigment is most 

 abundant in the cells about the apex of the refracting body 

 and less so towards its base, not appearing at all in any of 

 the cells that come out to the cuticle ; hence the appearance 

 the organ presents of lying beneath the cuticle. The oblique 

 position of the refracting body renders it possible to be com- 

 pletely enveloped by an epidermis not as thick as the body is 

 long, while making the line of vision very far from vertical 

 to the branchial surface. 



A similar section depigmented in Grenacher's liquid and 

 double stained in hematoxylin, followed by borax carmine, 

 gives a well-differentiated result in which cuticle, refracting 

 ingrowth, and the abundant connective tissue matrix are all 

 bright red, while the nuclei are blue, and the pigmented parts 

 of the epidermal cells faint yellow. Such a section of the 

 apical or innermost part of an eye is represented in Fig. 25, 

 showing clearly the pear-shaped terminal cell containing the 



