4 8 



E. E. JUST. 



do not form membranes after short exposures) may fertilize 

 perfectly we may assume that these particular eggs were on the 

 border line of proper exposure. Insemination, however, caused 

 no membranes (cf. Herbst) in the over-exposed eggs, and this is 

 always the case, though some of the eggs cleave. 



Membranes once formed may be removed, but after insemina- 

 tion these eggs develop no farther than uninseminated butyric 

 treated eggs. Study of the figures given in Table III. shows 

 first, that the cleavages of unshaken inseminated eggs (with 

 membranes) and of shaken inseminated eggs (without membranes) 

 are approximately equal; and second, that the per cent, of mem- 

 branes in A plus the per cent, of cleavages in B or C is very close 

 to a hundred. This must mean that eggs with membranes formed 

 with butyric acid are not fertilizable. In a given lot of eggs 

 exposed for the optimum time to butyric some are not completely 

 activated and have not formed membranes. These are the eggs 







that cleave following insemination ; the removal of the membranes 

 does not affect the per cent, of cleavages thus obtained. 



The experiment of July 8 part of which has already been 

 given (p. 40) is clearly decisive. Following exposure to butyric 

 sea-water Series A eggs were shaken and inseminated (series B) 

 with the results found in Table IV. 



TABLE IV. 



No. 



Exposure. 



Per Cent, of Membranes 

 (Series A). 



Per Cent, of Cleavage 



After Insemination 



(Series B). 



B? to 615: cleavages very abnormal; frequently incomplete many spindles 

 present. 



