186 The Philippine Journal of Science 1917 



darker. The process of pigmentation is much slower than the 

 change from dark to light effected by adrenalin. 



The area first darkened by the injection remained well defined 

 in several experiments, indicating a direct effect on the mela- 

 nophore cells, though positive pigmentation of the granules could 

 not be demonstrated when pieces of light-colored skin were floated 

 on chloretone solution under the microscope. Injection of 

 adrenalin or application of adrenalin to the surface of the skin 

 of chloretonized lizards gives the characteristic bleaching. 



DISCUSSION 



Investigators have heretofore described small pigment-carry- 

 ing granules in chromatophores and melanophores. Von Szily 

 refers to them as Pigmenttrdger and says : 



Die Umwandlung der farblosen Pigmenttrager im Pigment erfolgt wahr- 

 scheinlich unter dem Einfluss von spezifischen Zellfermenten. Die Letzteren 

 konnen ihre Wirkung auf das Chromatin, die Muttersubstanz des Pigmentes, 

 erst dann ausiiben wenn die Kernmembran normalerweise im Verlaufe 

 der Mitose zeitweise verschwindet, oder wenn einzelne Chromatinparti- 

 kelchen in der Teilungsruhe unter den eben beschriebenden Umstanden 

 aus dem Kern eliminiert werden. 



No other workers have referred to the colorless pigment gran- 

 ules, or farblose Pigmenttrager. Hooker and Spaeth seem con- 

 vinced that there exist in the cytoplasm elements that are capable 

 of combining and by some influence of the nucleus are trans- 

 formed into melanin granules. Hooker concludes that — 



In the cells of embryo frogs, melanin is formed from some substance 

 (probably t3n'osine or its derivatives) in solution in the c3rtoplasm when 

 acted upon by the nucleus (perhaps an oxidase reaction). 



What role is played by the nucleus in the production of the 

 pigment in the granules of the lizard we are at present not pre- 

 pared to state. However, studies are now being carried on that 

 may throw more light on this subject. If melanin granules be- 

 come pigmented by means of an oxidase, we can conceive also of 

 the gradual destruction and disappearance of the pigment by 

 chemical action. This process of destruction and production of 

 pigment explains the apparent "contraction" and "expansion" of 

 the melanophore in the lizard. 



Our experiments show conclusively that normally the coordi- 

 nate fading of the melanophore is due to a primary nervous 

 reflex, through stimulation of the retina, with probably a sub- 

 sequent production and liberation of a hormone, which is carried 

 about by the blood and lymph. What this hormone is we are 



