LIGHT PRODUCTION IN CEPHALOPODS. 1 75 



as known, the entire subfamily Taoniinae, are peculiar in that the 

 subocular photophores are reduced to one or at most two organs 

 which are frequently so large as to cover nearly the entire lower 

 surface of the eyeball. When two such are present they are semi- 

 circular or more or less crescentic in outline, the smaller or ante- 

 rior organ fitting into the concavity of the larger. The eye-organ 

 in Ctenopteryx is a single large falciform structure. In most 

 genera, however, the subocular photophores are smaller and more 

 diffuse in their arrangement, the commonest system being an 

 alignment in a simple, bead-like, longitudinal series on the 

 ventral periphery of the eyeball. Curiously enough, the series 

 usually includes organs belonging to two or more diverse 

 structural types. Such is the arrangement to be found in 

 Lycoteuthis, Nematolampas Abralia, Abraliopsis, Watasenia and 

 Enoploteuthis, the last-named genus having nine or ten organs 

 on each eye, all the other genera five. Liocranchia and 

 Pyrgopsis have four organs similarly located, but all of one 

 type. Chiroteuthis picteti and C. imperator are figured by Chun 

 as having three longitudinal chains of isomorphic organs, 

 22 to 29 in all, upon each eye. In the latter species he 

 found the number to be somewhat variable, which is an unusual 

 circumstance with the subocular organs. This is a particularly 

 striking fact when the remaining five genera having this type of 

 photophore are considered. In all of these, namely, Lampadio- 

 teuthis, Pyroteuthis, Pterygioteuthis, Cranchia and Leachia the 

 photophores of the eyes, varying in number from four in 

 Lampadioteuthis to fifteen in Pterygioteuthis giardi, have lost 

 their simple serial arrangement, and the individual organs are 

 scattered to a greater or less degree over the lateral as well as 

 the ventral region of the eyeball. Their distribution thus 

 becomes highly irregular, yet it is almost always absolutely 

 definite and practically invariable within the bounds of each 

 single species. Chiroteuthis veranyi, as described by Chun, is 

 unique in having two large bands of photogenic tissue on the 

 ventral convexity of each eye, accompanied by a few small 

 isolated photophores of the more ordinary form, by the coales- 

 cence of a number of which they perhaps originated. Since the 

 genera possessing subocular organs are all cegopsid, it follows that 



