348 H. M. BERNARD. 
seems no longer in a position to have much pigment pass out- 
wards through it, and, if any travels through, it probably passes 
right through without being even temporarily arrested, pre- 
sumably because the resistance of the retina to the passage 
of the pigment which in the functional eye is, according to 
the theory, the cause of the irritation and resulting sensation 
has ceased. In the same way the resistance of the retina to 
the entrance of the white matter observed in Uromastix has 
also ceased, so that it streams outwards through the cells in 
single shapeless or angular granules [which are of very differ- 
ent sizes, and have no resemblance to true pigment granules 
either in appearance or distribution], to accumulate at the distal 
ends of the degenerate retinal cells. Beyond this point they 
seem unable to travel. I know of no evidence which would 
lead me to believe that the coagulum in the cavity of the eye 
is due to any transformation of these granules; on the other 
hand, it is quite possible that it may result from the occasional 
passage and conversion into slime of true pigment. 
With regard to Leydig’s doubts! as to whether the pineal 
eye was ever an eye at all, his objections are based upon the 
very facts which, it seems to me, establish the point beyond 
dispute. He appeals to the presence of pigment in the lens. 
But this is exactly what we might expect in an eye going out 
of function. The pigmented cells ball together as they reach 
the free spaces among the retinal cells outside the palisade 
layer; then streaming through the retina they ball again on 
reaching the cavity of the eye, and may accumulate as globular 
masses against and within the lens.2 For some reason or 
other, as the eye ceased to function, the pigmented granules 
ceased to clarify on reaching the cavity of the eye, as they 
appear to do, say, in the eyes of molluscs, of Petromyzon 
(see below), on passing into the vitreous humour through the 
1 © Abh. Senk. Nat. Gesch.,’ xvi, 1890, p. 531. 
2 In some cases the pigment seems (in Spencer’s figures, |. c.) to be forcing 
its way between the lens cells; this we should imagine would be the most 
natural. It is not easy to understand why, in other cases, the cells should 
ball together in the heart of the lens. 
