38 bulletin: museum of comparative zoology. 



to the long axis of a cell, as is the case in the median eye; but there is 

 certainly a very definite grouping of these rods in the organs of Claus, 

 and within a group the rods are approximately parallel to each other. 



d. Relation of Nerves to Organs of Claus. — That the interior bodies 

 in the organs of Claus, as in the median eye, have some functional, if 

 not directly structural, relation to nerve terminations, is at least 

 strongly indicated by such conditions as are shown in Figures 19, 20 

 (Plate 2), 26, 29 (Plate 3). Figure 19 (Plate 2) is especially good for 

 showing this. It is plain that there is a large bundle of nerve fibrils 

 leaving one of the cells, and that, within the cell, the fibrils are ar- 

 rano-ed so nearlv in the same manner as are the interior bodies, that 

 one can scarcely resist the conclusion that they are interdependent, 

 even if the exact structural relations between the two are not apparent. 

 Likewise in Figure 20, the interior bodies lie directly in the path of the 

 fibrils which go to make up the large nerve {n.) leaving the cell, and 

 almost without exception, the long axis of the rod has the same direc- 

 tion as the fibrils. In Figure 51 (Plate 5) a relatively small nerve 

 may be seen leaving the cell, but here the interior bodies are not visible. 

 They appear in Figure 55, which is drawn from the section adjoining 

 that from which Figure 51 was taken. I have been unable to see that 

 the interior bodies and the nerve fibres are, in any case, structurally 

 connected, but such conditions as are shown in Figures 20 (Plate 2) 

 and 26 (Plate 3) oft'er almost unassailable evidence that their interac- 

 tion is closely concerned with the sensory function of the organs of 

 Claus. 



It is more difficult to ascertain the exact type of nerve-termination 

 in the organs of Claus than in the median eye. But I believe that the 

 type of ending is the same in the two cases, for I have seen in certain 

 preparations unmistakable evidence of nerve fibrils in a cell of the 

 organ of Claus, and they were in every way similar to those of the 

 retinal cells, except that the club-shaped enlargements were directed 

 toward the basal plate, instead of away from it. In these cells, also, 

 as in the cells of the median eye, I believe that the denser character 

 of the cytoplasm and the more or less evident striation, and radiate 

 arrangement of particles in the region of the basal plate, is evidence 

 of secretory activity and not of the presence of a " Stiftchensaum." 



Notwithstanding the absence of any experimental evidence as to 

 their function, I believe that the structure of the organs of Claus 

 warrants us in regarding them as eyes. The cells of these organs 

 correspond in every essential feature of structure with the retinal cells 

 in the median eyes, since they possess basal plates, interior bodies 



