244 



DAVENPORT HOOKER 



many observers for various animals and has been most recently 

 confirmed by Spaeth ('13) for the teleosts. 



When fully contracted, the living melanophore of the adult 

 appears as a rounded mass of pigment, no cytoplasm being visi- 

 ble. Expansion begins in much the same manner as in the 

 melanophores of the larvae. At first, thin streams of pigment 

 granules leave the mass on all sides, gradually growing larger 

 as they extend. Many such processes fuse together and some 

 are withdrawn. It is noticeable that, contrary to the condition 

 in the larvae, these pseudopodia do not coalesce to form a broad 



A B 



Fig. 3 Two corial melanophores from the skin of an adult Rana fusca. In 

 A, one, and in B, two of the branches of the cavity within which the cell lies are 

 shown. A is completely contracted, B only partially. In the latter, the cyto- 

 plasmic processes at each end of the mass are seen. 



sheet, but form elongated, rounded processes. As expansion 

 proceeds, the cell body continually decreases in size and when 

 the extreme is reached, is scarcely to be distinguished from the 

 processes themselves. During the latter part of exi:)ansion, the 

 processes lose their uncertainty of direction and always follow 

 the same course to form the individual cell pattern. An expand- 

 ing cell may, however, begin to contract at any stage, complete 

 or not, in which case the processes are withdrawn again into the 

 cell body. 



When fully expanded, the cell appears as a basket made up 

 of a large number of elongated, narrow, rounded processes, some 



