J. A. C. NICOL 321 



pigmentation the pigment granules are either aggregated or dispersed 

 within the cell. Is there any evidence that the photogenic granules 

 within photocytes can be similarly aggregated or dispersed under 

 extracellular influences? 



Dr. Nicol: There is no evidence at present available for hormonal 

 control of movement of photogenic granules. There is, however, the 

 interesting observation of the Greenes (1924) to the effect that injec- 

 tion of pituitrin (extract of posterior lobe of the pituitary) induces 

 luminescence in the midshipman (Porichthys). It is possible, although 

 conjectural, that intermedin, the melanophore-expanding hormone, 

 was the effective constituent in the extract. So far as I can determine, 

 the Greenes made only a single test and did not continue the work. 



As I recall. Dr. Haneda has made an interesting observation con- 

 cerning certain species of squid that possess a luminescent mantle 

 organ partially bounded by the ink sac (e.g., Euprymna). It seems 

 that movement of ink in the ink sac could be controlled in such a way 

 as to blacken or expose the surface of the light organ and thus 

 regulate light emission. 



