328 RUPERT VALLENTIN AND J. T. CUNNINGHAM. 



consists of straight fibrils in two bundles crossing at right 

 angles, and other bundles in other directions. In front of the 

 fibrillar mass are seen one or more flat cells which belong to 

 the cellular layer. In front of these is the biconvex lens (7., 

 fig. 1), perfectly homogeneous in structure, and highly refrin- 

 gent ; its diameter exceeds that of the fibrillar mass, so that it 

 rests on the edges of the cellular layer. In front of the lens 

 is a layer of cellular tissue, which contains a ring of circular 

 fibres, running round the edge of the lens. The cells of this 

 layer, which may be called a cornea, are much smaller and 

 more regular than those of the posterior cellular layer. 

 Between the fibrous ring and the posterior part of the organ, 

 outside the lens, is a kind of cle'ft occupied by a few small 

 cells, which separate the ring from the anterior edge of the 

 reflector. 



The red pigment of the cells coating the reflector disappears 

 in spirit, and the peculiar colour of the internal surface of that 

 layer cannot be seen in sections. The reflector and the fibrous 

 ring absorb carmine very slightly, and the only deeply-stained 

 parts of the sections are the cell nuclei. The organ is situated 

 immediately below the epidermis (ep., fig. 1), and connected 

 with it by cellular strands, which, passing in at the cleft be- 

 tween the edge of the reflector and the fibrous ring, place the 

 posterior cellular layer in structural continuity with the epi- 

 dermis. It is possibly by this cellular communication that 

 nervous impulses are conveyed to the organ. The organ is sur- 

 rounded by a blood space (lac, fig. 1), and the cellular strands 

 cross this space. In the thoracic organs there are also thin 

 bands of muscle passing across the space to be inserted in the 

 surface of the organ, but we have not found such muscles con- 

 nected with the abdominal organs. The subneural artery 

 passes between each of the abdominal organs and the pair of 

 nerve ganglia which lies close to it dorsally. 



The structure of the photospherion of the ocular peduncle 

 differs considerably from that of the rest. The difference con- 

 sists in the absence of the lens, and of the cornea as a separate 

 and distinct layer. The organ (fig. 3) is continuous with the 



