144 University of California Publications in Zoology [Vol. 11 



Similar differences on this point occur among workers on 

 the chromatophores of fishes, reptiles and various invertebrates. 

 Loeb's (1899) observations on the migration of pigment cells in 

 the yolk sac of Fundulus indicated that these cells were amoe- 

 boid, as Heineke (1880) considered them to be in Gobius and 

 Syngnathus. Ballowitz (1893) finds that in the herring the 

 terminal cell processes of the retracted melanophores are free 

 from pigment, and he concludes that there is no amoeboid 

 movement of the cells, but only "ein Ausstromen und Zuriick- 

 stromen der Pigmentkornchen in dem unverandert liegen blei- 

 benden Protoplasma. " Zimmermann (1893) and Solger (1890) 

 maintain the same view, and Franz (1908) who studied the 

 movements of pigment cells in the fins of various young fishes 

 where they can be seen with exceptional clearness in the living 

 animal, attributes the greater part of the changes to movements 

 of granules within the cell, although he does not deny that 

 changes in the outline of the cell may occur. 



The foregoing may perhaps suffice to indicate the state of 

 opinion regarding the movements of chromatophores in the 

 vertebrates. A general discussion of the literature of the sub- 

 ject will not be attempted, especially since it has recently been 

 reviewed by van Rynberk (1906). I may mention, however, an 

 observation made more or less incidentally by Harrison (1910) 

 in the course of his valuable investigations on the outgrowth of 

 nerve fibres from the neuroblasts of frog embryos. Pigment 

 was observed to increase in some of the cells of a frog embryo 

 that were kept in lymph, and "the individual cells changed 

 slightly in form". The changes in one cell were sketched at 

 intervals of two or three days. Harrison 's account rather implies 

 that these cells were not isolated from the surrounding tissue, 

 and the relation of the pigment to the processes of the cell was 

 not described. 



While studying the behavior of small pieces of the embryos 

 and larvae of Hyla regilla when cultivated in hanging drops of 

 blood plasma or serum, I observed that the pigment cells some- 

 times wandered away from the rest of the tissue and became 

 entirely isolated. Epithelial cells and connective tissue corpuscles 

 were frequently seen to behave in a similar manner, especially 



