GEORGE 5. R l h Y I TIM 7Vistar Institute of A~iatoniy and Biology ONE PLATE INTKODUCTION Beiiike(l9) was tlie first to point out clearly that the pigment graiiiiles of animal cells are composed of two constituents, a n organic substratum, the 'Pigmentgrundsubstanz' or 'Pigmenttriiger,' as tlie German authors call it, and a coloring matter, melaniri or fuscin. The latest investigations have confirmed Reinke's findings, arid it is now known, ill addition, that tlie ultimate pigment granules develop only gradually out of colorless earlier stages. This process is, liovever, by no means so simple as described by von Szily (23). Xiescher (li) in particular lias recently pointed out how complicated is this process of pigment formation. According to the present status of our knowledge, we can regard as definitely certain only tlie fact that during pigment formation in embryonal cells probably a multitude of factors cooperate, only two of these being known to us so far, and they only approximately. One is an oxidizing f erment, first discorered by Bertrand( 1) in plant tissues and described a s tyrosinase. Recently this lias been thoroughly investigated by Bloch and his collahorators in animal tissues. The second factor is regarded as an organized body, a morphological constituent of tlie cell, a sort of granular body designated by several authorities as 'Pigmentbildner. ' Since the nature and origin of the latter have not been explained up to the present, I have subjected them to as thorough a morphological 413 JOLRKAL O F M O R P H O L O O P AND PHISIOLOC:P, XOli. 3 9 , NO. 2
'l'lie statements in tlie literature of the subject coiicei*iiin,g the origin of the pigment granules show a wide divergence. Most authors are of the opinion that the pigment originates from some one of the iiuclear substances. The chief exponent of this opinion is voii Szily, wlio treats this siibject in an extensive monograph. He describes filamentous formations iii Others :ire sliowing gr:inul:ir tlisintegr:cticin.