PINEAL EYE IN LAOEBTILIA. 209 



eye ; the connective tissue enclosing it being omitted for the 

 sake of clearness. 



Structure. — In shape the eye resembles more than any- 

 thing else a hemisphere^ the equatorial plane being occupied 

 by the lens, which is, in shape, almost concavo-convex, its 

 outer, anterior surface being flattened. The bulb is encased 

 closely by the connective tissue of the dura mater (Z). M.), a 

 thin layer passing in front of the lens, whilst all the posterior 

 surface is surrounded by^branched pigment cells [pig.^). 



Lens. — The lens has the usual cellular structure, being 

 thinnest round the margin where it is continuous with the 

 retina ; the nuclei of its component cells form a well-marked 

 layer running across it in section from side to side. 



Retina. — Within the retina a considerable deposition of 

 pigment in various parts indicates, to a certain extent, degen- 

 eracy, and at the same time renders the examination of its 

 structure difficult. 



The rods [R) are well marked, and in places present the 

 appearance of being striated. Two bundles of rods are slightly 

 elongated {R^)-> being in connection with two distinct nervous 

 strands entering the retina posteriorly. External to the rods 

 lie spherical nucleated elements arranged in two layers, an 

 inner {n}) and an outer (w^), whilst amongst them much 

 pigment is scattered in small granules, rendering their detec- 

 tion difficult; in parts still larger masses of pigment are 

 present, which may perhaps be due to the degeneracy of the 

 spherical elements into pigment-bearing cells. 



Epiphysis. — As before said, two distinct nervous strands 

 may be seen entering the retina posteriorly and close together 

 [ne), one being larger than the other; back from these two, 

 which soon unite, may be traced a single nervous strand which 

 it is extremely difficult to follow, owing to its close investment 

 by connective tissue of the dura mater, but which I believe 

 runs downwards and backwards until it joins the proximal 

 part of the epiphysis {Ep.), which is considerably swollen and 

 has a curious development of pigment in its walls. 



Along with the pineal stalk runs the usual blood-vessel, 



