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and in each indentation there is a delicate bundle of hair- 

 like " Stiftchen " (fig. 47, Si. s.), which appear to break 

 away from the cells in macerations. Thus the eye of 

 Buccinum agrees with the long series of eyes possessing 

 Stiftchen-bearing cells. The presence of such processes 

 is one of the most striking characters in the structure of 

 visual organs. 



There has been no small difference of opinion as 

 to which are the visual cells in gastropod eyes. In 

 many cases the difference between the cells which has 

 struck the observer has been the presence or absence of 

 pigment. Here both sets possess pigment. Could 

 the actual nerve connections be demonstrated, the 

 matter would be easily solved, but unfortunately the 

 fibrous processes of both cells merge into the tangled mass 

 of nerve fibres and connective tissue below the eye. 

 Judging from structures in the eye of Pecten, and 

 especially from the character of the nucleus, the author 

 would say that the large cells are the visual cells not- 

 withstanding the fact that the cell body of the slender 

 cells is more in accordance with expectations. 



This view is, however, supported further by two 

 facts. The large cells appear to possess the " Stiftchen." 

 Both kinds of cells occur laterally almost up to the inner 

 cornea. There the large cells begin to disappear, whilst 

 the nuclei of the others are very like, one might almost 

 say the same as, those found in the cells of the inner 

 cornea itself. According to this view, therefore, the 

 slender cells are merely supporting cells, and they are 

 continued across the eye to form the inner cornea. 



The nuclei of the inner corneal cells are flat 

 compressed structures (fig. 47, Ps. cor.), like the nuclei 

 in the retina, but instead of being arranged at right 

 angles to the wall of the cavity they have rotated, so 



