THE DIVIDING SEA-URCHIN EGG 
295 
the favorable concentration for this alcohol, while the solutions 
on either side are slightly hypo- and hyper-toxic respectively; 
that is, in the one case practically all eggs survive to the blastula 
stage, and in the other nearly all die. Recovery of resistance 
after the first division appears to be relatively slow. When the 
percentage of surviving blastulse is plotted against the time inter- 
vals, regarding as typical the data of the 0.07 vol. per cent 
solution, an interesting curve (see figure 51 below) is obtained 
HEfTYU ALOOiiOL. 
pucrr OP TUE coAvc op suscefri%LE and i^€Si5TA«rr Phases of tac 
S5A-U«iCMiK KCS WHIN SUfelEClea To O.cnv'OL.FE?^ CEfff HEfTYU ALCOHOL 
miN^ES ATTfclfMiilftff INTERVALS AfTeRffefcTiUiArieN; 
The Per cenTof sorviVino BiAsTyiAe ijPvoTreq intcrvais, 
OS IN* fo<Eto»i<»f»»fcwe£Tkt «F Each BlTE WtNwTe TfeRioO. 
which is fairly comparable with the one shown for i-Amyl alcohol. 
There is a gradual rise in resistance up to the period of first cleav- 
age, with a sharp drop during cell-division followed by a slow 
recovery. 
OCTYE AECOHOL 
Normal octyl alcohol apparently is considerably more toxic 
than its isomere capryl alcohol. In a series of five experiments 
with octyl alcohol in concentrations ranging from 0.010 to 0.030 
vol. per cent, the best concentration for exposures of five minutes 
