Vol.. 8, 1922 
ZOOLOGY: L. C. WYMAN 
129 
in this way showed a distal migration in from five to fifteen minutes 
wherever the ether solution touched the skin. As controls in each ex- 
periment eyes of unetherized fish that had been kept either in the light 
or in the dark were prepared . 
The condition of the retinal melanophores of fish which had been ether- 
ized, either by applying the solution to the gills or to the bod}^ differed 
in no way from those of normal fish kept under the same conditions of il- 
lumination. Those of light fish showed a distal and those of dark fish a 
proximal migration of the pigment granules. Ether was applied di- 
rectly to the eyes by immersing excised eyes in a 5% solution for thirty 
minutes followed by immediate fixation. Very commonly the pigment in 
eyes which were treated in this way was extremely contracted and broken 
up into rather large round masses separated from each other by spaces 
much larger than any seen in normal eyes. This was probably a post 
mortem change due to the disintegration of the pigment cells. In eyes 
which appeared normal, however, the condition of the pigment was not 
different from that of retinas which had not been treated with ether. The 
post mortem change described above was often seen in eyes whose optic 
nerves had been cut before the application of ether. Here too the pig- 
ment cells did not seem to be affected at all by the ether. 
Arey ('16) found that carbon dioxide and ether, both in darkness and in 
light, and in excised as well as in undisturbed eyes, completely check the 
movement of all the retinal elements in fishes. The retinal pigment of fishes 
anesthetized under one condition of illumination and then removed to 
another remained in the condition characteristic of the first state of light 
or darkness. Hence I conclude that ether does not have an action on the 
pigment cells of the retina in fishes the reverse of that of adrenalin. It 
merely arrests the retinal pigment in whatever condition it happens to be 
when the drug is administered. 
An explanation for the differing effects of adrenalin and ether upon the 
scale and retinal melanophores in fishes may probably be found in the 
widely different methods of control of the two types of melanophores. 
The scale melanophores are controlled by the sympathetic nervous sys- 
tem and in the light they are held in the contracted condition by means of 
a tonus established by impulses in the central nervous system set up by 
light stimuli received through the eyes. The contracted state, then rep- 
resents a state of stimulation. vSpaeth ('16) thinks that melanophores are 
a physiologically modified type of smooth muscle tissue. Adrenalin, the 
effect of which upon smooth muscle tissue is comparable to sympathetic 
stimuli, causes a contraction of scale melanophores. Ether anesthetiza- 
tion removes the nervous tonus and allows the melanophores to expand. 
The melanophores of the retina, however, are not controlled by means of 
*retino-motor' nerve fibres (Arey, '16, p. 180), but their activities are simply 
