64 W. J. DAKIN. 



the pigment-mantle. 'i'liey are usually constricted in the 

 middle, so that they appear hour-glass-shaped in section, an 

 intercellular space being left between them (PI. 7, figs. 4 and 

 10). Externally there is a very distinct striated cuticle 

 (PI. 7, fig. 10, Cut.) which forms a hexagonal plate over the 

 cell, and if the cornea is carefully focussed down upon from 

 above these hexagonal plates are seen with their edges in 

 close contact forming a definite mosaic (PI. 7, fig. 3). If the 

 corneal cells ai'e now brought into focus at about the level 

 of the nucleus, they appear still hexagonal in section though 

 rather irregular, and the cell-walls do not touch. The spaces 

 left between the cells on each side are crossed by numerous 

 intercellular bridges (PI. 7, fig. 4). I have no doubt 

 that these are what Patten took to be interlocking processes 

 of the cells. Carriere (26) was the first to discover their true 

 nature, but asserted that Patten could not have seen them at 

 all, since they were finer than his interlocking processes. 

 Schreiner (30) stated that the intercellular spaces were filled 

 with a pi'ominent cement substance which, through shrinkage 

 dui'ing fixation, caused the appearance seen by Patten, and 

 does not mention any intercellular bx'idges whatever. Rawitz 

 was also of the same opinion and does not refer to Carriere's 

 statement (Rawitz [25], p. 109). I have seen them quite 

 distinctly in the pigmented cells of the pigment-mantle as 

 well as in the cornea, and they have the same structure in 

 both places. There is another detail to be mentioned here 

 which illustrates the difficulties caused by artefacts. Patten 

 stated that the corneal cells had basal processes like the 

 lateral ones, but which were longer and penetrated the 

 underlying connective tissue, reaching the lens. This has 

 been denied by all investigators since, and I had seen no 

 traces of any such structures in hundreds of sections examined. 

 After using the Bielschowsky-Paton silver method, however, 

 the result figured (PI. 7, fig. 10) was obtained. The tissues 

 were fixed in 4 per cent, formol and lay in 1 per cent, silver 

 nitrate solution for three weeks, which one might say was a 

 likely method for artefacts. On the other hand, the structures 



