MELAXOPHORES OF RAXA 239 



ergibt, dass dort, wo in der Expaiisionsphase die Auslaufer der 

 spinneiizellenartigeii Chroiiiatophoren sich befunden hatteii, niin- 

 iiiehr eiii Kanalsystem erschcint " ( ' 10, pp. 433-434) . It is strange 

 that the fixed space, within which the amoeboid cell expands 

 and. contracts, should have been interpi-eted for such a long time 

 as a fixed cell. 



In connection with some work on the color changes of adult 

 Rana fusca in the absence of nervous control (Hooker '12j, it 

 was noted that the melanophores of this animal occupy pre- 

 formed spaces. At that time it was not possible to follow up 

 this observation as fully as it deserved. The present paper 

 gives the results of further investigation into the mechanics of 

 ])igment movement in both lar\'al and adult frogs. 



Rana fusca and R. pipiens furnished the adult, and tadpoles 

 of Rana pipiens the larval, material used. Over a hundred 

 series of observations w^ere made on the living corial melano- 

 phores of tadpoles and adult frogs and preserved material from 

 both was examined microscopically. Meve's solution and cor- 

 rosive-sublimate-acetic mixture were used as fixing agents, the 

 preparations being later stained in Ehrlich's hematoxylin and 

 Congo red, iron hemotoxylin or gold chloride, or were examined 

 unstained. 



THE -MELAXOPHORES OF TADPOLES 



The melanophores, which will later come to lie in the corium, 

 first make their apj^earance in the larvae of Rana pipiens, which 

 are 10 to 12 mm. long. They are situated in the subepidermal 

 connective tissue throughout the body and are particularly nu- 

 merous in the head and back of the tadpole. Those in the head 

 are especially well suited for investigation, as the living tadpole 

 is trans]3arent in this region of the l)od>' and as the sheet of 

 connective tissue in which these cells are found may easily be 

 dissected out for nncroscopic study. The melanophores of frog 

 Iar\'ae may readily be examined at high magnifications as they 

 lie nearly in one plane, even when expanded, and parallel to the 

 surface of the body. They will be referred to as the connecti\e 



