39 WILSON GEE. 



of the egg membranes. Also the nuclear material must be more 

 deeply imbedded in the cytoplasm than in an earlier period, 

 and thus less in position to be affected. 



The treatment of the lot of eggs used at this time show that 

 even the ten and fifteen per cent, solutions acting for a half hour 

 do not produce a much greater effect than do the two per cent, 

 and five per cent, solutions at an earlier period after fertilization. 

 In the treatments for one hour, the fifteen per cent, and twenty- 

 five per cent, solutions show a considerable effect in reducing the 

 percentage developing; particularly is this true in the case of the 

 latter concentration, which killed all of the eggs except six. 

 Even with this rigorous treatment two individuals of the six 

 went through to the sixth day as normal individuals and from 

 all appearances would have hatched in about the normal time. 



While the data at hand are not as extensive as perhaps might 

 be desired, it seems safe to draw the conclusion that the eggs of 

 Fnndulus are very susceptible to toxic effects shortly after 

 fertilization and become more resistant as development proceeds. 



4. Effects of Dilute Sodium Hydroxide Solutions. 

 In several instances eggs were treated with dilutions of a 

 standard alkali solution. The results show in some instances 

 a large percentage of defective individuals from concentrations 

 as low as N/^oo, N/^oo, and N/8oo NaOH. The percentage of 

 fertilizations is considerably lowered as the result of such treat- 

 ments, and many aberrant cleavages occur. The effects in this 

 connection, however, seem very variable and the time was not 

 available for more than a few experiments, the data from which 

 permit of no decided conclusions further than that some eggs 

 are markedly affected in their development by treatments of low 

 concentrations of alkali solutions. During last summer a lot of 

 eggs treated with several drops of a very dilute solution of sodium 

 hydroxide (0.6 c.c. N/io NaOH + 50 c.c. sea water) for only 

 fifteen minutes at twenty-five minutes after fertilization produced 

 a large percentage of striking defects. One of the individuals 

 of this lot is figured in the text (Fig. 14). The evidence is 

 sufficient to state that the eggs of Fundulus in some instances 

 in the more critical periods in their history before and after 



