E. NEWTON HA31VEY 295 



From the evidence in Table III it would seem that Cypridina luci- 

 ferase will only give light with the luciferin of a very closely related 

 form, Pyrocypris, a genus that differs from Cypridina only in the 

 character of appendages on the upper lip. Both genera belong to 

 the family, CypridinidcB. Crosses of Cypridina luciferase with the 

 luciferin of Odontosyllis, Pholas, or fireflies, all of which possess a 

 luciferin-lucif erase reaction, gives only negative or very faint positive 

 results as does the reverse mixture, Cypridina luciferin crossed with 

 the luciferase of these other forms. All my attempts to oxidize 

 Cypridina luciferin with oxidizing enzymes or oxidizing agents of 

 various kinds have failed, and also all attempts to oxidize with light 

 production, various easily oxidizable substances with Cypridina luci- 

 ferase.^ We must therefore conclude that these two substances 

 responsible for the production of light by Cypridina, are specific to 

 the highest degree. 



SUMMARY. 



Among sixteen groups of luminous forms investigated by the author, 

 in only four (fireflies, Pholas, ostracods, and Odontosyllis) is it possible 

 to demonstrate the luciferin-luciferase reaction. In many groups this 

 is probably due to the smaU amount of these substances present in 

 the luminescent organism or to their instability. In the medusae and 

 pennatulids, despite a large amount of luminescent material, luciferin 

 and luciferase cannot be demonstrated. This does not appear to be 

 due to the presence of luciferin and luciferase in equivalent proportion, 

 or to their instabiHty. In fact, one is led to the conclusion that 

 luciferin and luciferase do not exist in these forms, but such a con- 

 clusion must be regarded as merely tentative, in view of the funda- 

 mental character of the luciferin-luciferase reaction. Luciferin of one 

 form will not luminesce with the luciferase of another form or vice 

 versa, unless very closely related (Cypridina and Pyrocypris). All 

 experiments emphasize the specificity of the light producing sub- 

 stances of Cypridina. 



* Harvey, E. N., /. Gen. Physiol, 1918-19, i, 269. 



