26 FRANK R. LILLIE. 



If the exposure to butyric acid is not sufficient to produce the 

 membrane reaction after transfer to sea water the eggs are mostly 

 fertilizable as though they had not been exposed to the acid. If 

 the reaction after transfer to sea-water is incomplete, so that 

 membranes are not fully formed, some eggs retain a certain 

 amount of capacity for fertilization after the membranes are 

 removed so that they may segment; they do not, however, pro- 

 ceed far with the developmental process under such circum- 

 stances, rarely to the gastrula stage. Moreover, the eggs of any 

 lot are variable, within rather narrow limits, with respect to the 

 degree of reaction after any given exposure. It would therefore 

 hardly be expected that all eggs of any given lot would give the 

 optimum membrane reaction after any given exposure, and one 

 would expect a certain minimal capacity for segmentation after 

 superimposed insemination with the best possible lot of eggs. 



Even in Loeb's experiments the outstanding fact is not the one 

 that he emphasizes, viz: that a certain percentage of eggs may 

 segment after superimposed fertilization when the membranes are 

 removed, but that most of the eggs do not do so. Loeb reports 

 as high as 20 per cent, segmentation after such a superimposed 

 insemination ; 80 per cent, of the eggs even in this case had be- 

 come unfertilizable, and this is the significant result. I have 

 never obtained such a high percentage of segmenting eggs in any 

 of my experiments after the optimum exposure, and my con- 

 clusion is that in this particular experiment of Loeb's the eggs 

 were on the whole under-exposed to butyric acid. I am strength- 

 ened in this opinion by the fact that he reports that the develop- 

 ing eggs formed normal larvce (1915, p. 261), a result that is 

 never obtained, in my experience, after an optimum exposure. 

 The experiment in question is reported as though only one ex- 

 posure time were used, in which case it would be a matter of 

 good fortune to hit the exact exposure time. In my experiments 

 at least three exposure times were always used by transferring 

 lots of eggs to sea water at 15 second intervals before, at, and 

 after the estimated time of optimum exposure ; then treating the 

 entire series. 



Reference should be made to the tabulated results of the prin- 

 cipal experiments (pp. 29-31) for the following discussion: 



