Effect of Alcohol and Ansestheties. 391 
is not infrequent. These conditions of the central nervous sys- 
tem might result from any cause that tends to retard development 
and are not particularly characteristic of anesthetic solutions 
as the eye anomalies are; yet the defects of the central nervous 
system are commoner in these anesthetics than in any other solu- 
tions with which the embryos have been treated. 
2. Chloretone, chloroform and ether induce much the same 
structural deformities in these embryos as does alcohol. They 
act, however, as more general anesthetics, causing a retardation 
in development. The characteristic eye and ear defects are not 
nearly so common, though they do occur as a result of treatment 
with these three substances. 
3. The effects of Mg on the developing fish’s egg have been 
previously considered. This substance is even more local in its 
action than alcohol, the principal defects resulting from its use 
being various anomalous conditions of the eyes, whereas the ner- 
vous system generally may be in many cases structurally normal. 
The embryos on hatching from the egg are able to swim in the 
usual manner and live for more than one month in aquaria, which 
is as long as any effort was made to keep them. The latter fact 
would seem to indicate that the nervous system also functionates 
normally. 
Magnesium was used to test at how late a period in develop 
ment the eggs might be introduced into the solutions with the sub- 
sequent development of the cyclopean condition. It was found 
that after normal development had proceeded for two, four, six, 
eight, ten, eleven, twelve or even fifteen hours, if the eggs were 
then placed in MgCl,, solutions, many of the resultiny embryos 
showed the cyclopean defect. At fifteen hours the eggs have 
reached the periblast stage and the blastodem is flattening down 
upon the yolk. The germ ring arises shortly after this time and 
begins its downward growth over the yolk mass. 
Whenever eggs are allowed to develop beyond the fifteen hour 
period before being introduced into the solutions of MgCl, they 
invariably give rise to normal two-eyed individuals. The occur- 
rence of cyclopia is less frequent when eggs are subjected at later 
stages than when introduced into the MgCl, solutions during the 
four or eight-cell stage. This is doubtless due to the fact that a 
