50 H. M. BERNARD. 



Here^ then, we have the very phenomenon we anticipated in 

 the event of the refractive matter which passed from the 

 outer into the inner h'mbs not being able to escape from the 

 latter, at least as fast as it accumulates. These inner limbs 

 become swollen with refractive matter. That this is the true 

 explanation of the " giant cones " is rendered clear by a study 

 of large fish like the cod. While in some, especially smaller 

 fish, the matter filling the inner limbs is often difficult to 

 define, in the sections I possess of the retina of an old speci- 

 men of this fish ^ the refractive matter is quite recognisable. 

 It is often seen in round homogeneous pellets just inside the 

 transverse membrane, and usually continued some way up the 

 axis of the inner limb. Round the periphery the contents 

 are more granular. Here and there, however, the whole 

 inner limb is one smooth, bright, homogeneous mass. These 

 smooth, I'ound, refractive pellets, which seem to accumulate 

 above the transverse membrane, may be compai-ed with the 

 refractive globules in the cones of the frog. The refractive 

 matter here, as elsewhere, is deeply coloured by plasma 

 stains, such as eosin, but easily gives up nuclear stains. 



If further evidence were wanted that the material which 

 swells the inner limb is the refractive matter absorbed from 

 the pigment granules by the outer limbs, it is supplied by 

 those cases in which the colour of the absorbed matter is the 

 same as that of the pigment. Such cases may be purely 

 individual differences, and depend upon chemical variations in 

 the pigments, or, perhaps, may be due simply to a too rapid 

 absorption. Certain it is that though the shape of the pig- 

 ment granules is lost, the colour of the absorbed matter may 

 now and then be hardly altered. Among my sections of the 

 plaice,2 for instance, there is one in which the strong reddish 

 colour of the pigment only slowly vanishes. It pervades all 

 the outer half of the swollen inner limbs, sometimes extending 

 some way up the " rod fibres." Other more striking instances 



' Fixed wit.li corrosive sublimate. 



^ Specially fixed and preserved for me by my lamented friend Mr. Martin 

 Woodward at the Plymouth Marine Laboratory. 



