INTEGUMENT OF NECTURUS MACULOSUS 525 
unchanged. Spaeth also holds to the theory that the chromato- 
phores are fixed stellate cells, and recently (’16) he has brought 
forth considerable evidence to prove that the melanophores of 
fishes and Amphibia are not connective-tissue cells, but modified 
smooth muscle cells in which the motor function is lost and a 
modified motility, migration of pigment granules, is developed. 
2. In Necturus. In Necturus, owing to- the thickness of the 
skin, it was not possible to observe the movement of pigment 
under high magnifications, as Kahn und Lieben (’07), Winkler 
(10 b), Spaeth (16), and others have done. In material fixed 
and mounted whole, cells in various stages of contraction were 
studied. In many eases practically all the pigment was massed 
within the cell body, but occasionally enough was left scattered 
through the tissue to outline faintly the extent of the cell in the 
fully expanded condition. In other places, isolated clumps of 
pigment were seen lying some distance from the contracted cells 
as if they had been left behind when the main mass moved 
proximally. 
It does not seem possible to reconcile these conditions with 
Hooker’s theory of amoeboid movement. If the pigment in 
contraction is carried proximally in the cytoplasm by pseudo- 
podia, none could be left behind, unless it escaped from the cell 
processes as they were being withdrawn. The appearance would 
be more readily explained by Spaeth’s hypothesis, that the 
‘contraction’ of the melanophore consists of an aggregation of 
the disperse phase of the melanin granules. In such coagulation, 
it is evident that scattered granules might be left in the processes 
of the cells and, if minute obstructions were present, the proximal 
movement might be hindered locally and the granules would 
collect at these points to form small clumps of pigment. In 
sections of contracted melanophores, however, it was not possible 
to distinguish empty cell processes. 
