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IOWA ACADEMY OF SCIENCE Voi.. XXVII, 1920 
susceptibility than those just described for i-amyl alcohol. The 
eggs apparently maintain throughout the cycle a relatively high 
resistance to the concentrations of hexyl alcohol here used, with 
only a slight increase of susceptibility at the time of first cleav- 
age; in the one case (D.!? voL per cent) there is evidence of a 
slight return of resistance just afterwards, and in the other (0.13 
voL per cent) there is not. Why there should be this difference 
in the behavior of the two alcohols is difficult to explain. The 
exposures to hexyl alcohol were perhaps insufficiently prolonged 
to bring out a well marked differential effect at the different 
stages of the cycle. Again, it is well known that certain anes- 
thetics are less effective than others in suppressing the cell-division 
process ; also many neuromuscular responses react differently 
to a given anaesthetic in different animals,. and in the same animal 
at different ages. Thus Lillie found chloretone much less effec- 
tive than chloral hydrate in suppressing cleavage in Arbacia eggs. 
As regards the alcohols that he tried, he lists propyl, butyl, amyl 
in the order of increasing favorability, while ethyl and capryl 
show a higher toxicity than others.^^ It may be that differences, 
both qualitative and quantitative, in the lipoid elements of the 
tissues, and hence in the plasma-membrane, form the basis of the 
observed physiological difference. 
In the controls which were running parallel to these experiments 
just described, a majority of the eggs entered the two-celled stage 
at about fifty-eight minutes after fertilization. At sixty-five 
minutes after fertilization, between 85 and 90 per cent had 
cleaved. Practically all eggs in the controls had reached the blas- 
tula stage the following day. 
HEPTYL ALCOHOL 
A series of six experiments was performed with this alcohol 
to determine the limits of suitable concentration. Reasoning from 
the data in the preceding, it was thought that the optimum con- 
centration would be between 0.04 and 0.07 vol. per cent, but to 
make sure, concentrations as low as 0.02 and as high as 0.08 vol. 
per cent were used. As a matter of fact, solutions of 0.06 and 
0.07 vol. per cent were found to be the best suited to the experi- 
ments, although it is interesting to note that even weaker solutions 
showed marked toxic action on eggs at the time of formation of 
the first cleavage furrow, while during the stages preceding and 
succeeding division, they had relatively little influence. Briefly 
summarizing, the results show that 0.07 vol. per cent approximates 
