MELANIN COLOR FORMATION. 329 



phenomena observed by Tornier are viewed in the light of the 

 work of Bertrand, it seems certain that in these two sets of phe- 

 nomena we are really dealing with the same facts. 



Tornier found that tadpoles divided into lots for differential 

 feedings gave (i) little or no pigment in the ones fed the mini- 

 mum, and progressively more pigment as the maximum is ap- 

 proached ; (2) a series of colors : u'/iite, yellow, red, gray, black. 

 Tornier concludes ('07^, p. 288) : It is possible, therefore, by 

 adjusting the dosage of fleshy food to force the epidermal color- 

 ation of Pelobates larvae (he elsewhere describes this as true for 

 other amphibia) into white, yellow (see p. 285), red, gray, black. 1 

 It will be seen that the types of color and the order of their ap- 

 pearance in the organism - - when we put these organisms into 

 such conditions as will force them to do the work of pigment 

 formation (oxidation) in stages closely follow the lines of our 

 purely chemical experience. Tornier produces entirely compar- 

 able effects upon the coloration by two other means, viz.: by re- 

 moving more or less yolk from the vegetative pole of the egg 

 through an opening made by a needle ; or by coagulating in situ 

 a part of yolk proteid by the introduction of water ; such coag- 

 ulations of yolk proteid cannot be digested by the develop- 

 ing embryo. The three methods employed all reduce the nutri- 

 tion of the animals, and produced albinism, erythrinism, black- 

 ness, or melanism, depending upon the state of nutrition. 



It was further found ('07) that the experiment could be carried 

 out in the opposite direction as well ; that is to say, the highly 

 fed, black-containing, and black-producing larvae of large or 

 small size could be made, through a diminution of feeding, to 

 produce a series of colors in the order of: black, brown, red, gray, 

 i^'Jiite. Certain observations by Powers ('08) are confirmations 

 of Tornier' s L results. 



Without extending these illustrations it can be stated that if 

 these facts and experiments mean anything they mean that in an 

 animal that produces melaninic color, there exists all the machinery 

 necessary to produce a series or scale of these colors. And that 



1 The proof that all these shades of color in Tornier' s tadpoles were melanins is 

 hardly as complete as is desirable, since lipochromes and traces of guanin are also 

 known to develop normally in late larval and adult stages of these amphibia. Many 

 facts, however, indicate that the colors here described by Tornier are true melanins. 



