176 APPENDIX. 



becomes evident that the large, obscure round spots correspond to the 

 central part of the digitiform lobes of Targioni Tozzetti ; that is to say, 

 to the cylinders constituted by the matrix of trachea (Tracheenendzellen 

 of M. Schultze), whilst the luminous part is represented by the parenchy- 

 mentous cells, and the little obscure spots are due to nuclei of these same 

 cells. Still towards the limit of the brilliant and obscure regions of the 

 luminous organ a very varied spectacle is observed. . . . 



" From all the facts which we have just described, one may conclude 

 with full certainty that the light of the Luciola has its seat in the 

 parenchymentous cells of the luminous organ. 



" It remains to be seen if the luminous combustion does not also take 

 place, though, with luminosity in other parts. In my previous work I 

 had it that the surface of the cylindrical lobes formed by the matrix of 

 the tracheae was the principal focus or seat of the combustion. The 

 facts which result from later observation oblige me to abandon this 

 opinion. . . . 



" In the moments of mean luminous activity, one may say that the 

 combustion is situated exclusively in the parenchymentous cells of the 

 superficial layer of the luminous organ." 



39. PAGE 73. Gammarus caudisetus, Gammarus longicornis, Gam- 

 marus truncatus, Gammarus heteroditus, Gammarus crassimanus. Cyclops 

 exiliens is also luminous. 



40. PAGE 77. Another species in which this change had taken place 

 is GalatJiodes antonu, an allied form which is shown in the central figure 

 of the frontispiece. Many more, as Willemcesea, Pentacheles, Polycheles, 

 and others, have organs of vision, which have undergone more or less 

 change. It has been suggested that certain deep-sea crabs, as Geryon 

 tridens, Gonoplax, Donychus, and Munida, have phosphorescent eyes. 



In Ptycogaster formosus (Plate XIII., Fig. 1), we find an interesting form, 

 living at a depth of twenty-eight hundred and fifty feet, or more than half 

 a mile, from the surface, which is provided with well-developed eyes. 



41. PAGE 81. The individual zooids, amounting to many hundreds, 

 are grouped in whorls, their orifices so arranged that the inhalent are 

 upon the outside of the cylinder, and the exhalent upon the interior. 

 Each animal draws in a current from the outside, ejecting it into the 

 interior ; the result of this volume of water rushing from the open end 



