152 CARL RICHARD MOORE. 



though the eggs were given as nearly as possible an exact equiva- 

 lent shaking as the first, yet 55 per cent, of them possessed in- 

 tact membranes. The membrane becomes very much toughened 

 shortly after production and a much greater amount of mechani- 

 cal agitation is necessary to destroy it. 1 



Even though many eggs are broken to pieces during the 

 shaking process and the solution becomes very highly colored 

 from escaping pigment, yet the eggs remaining intact appear in 

 good condition, not different in appearance from normal un- 

 fertilized eggs. The shaking has not materially affected their 

 developmental capacities; when such eggs are subjected to a 

 hypertonic treatment one can obtain from 35 per cent, to 40 

 per cent, of swimming larvae. 2 



Observations are entirely limited to experiments in which 

 eggs possessed large full membranes, and to lots of eggs that 

 showed a high percentage of membrane production. All other 

 sets of eggs in which membrane production was not of the best 

 were discarded. At variable times of the season short periods 

 appear during which it is very difficult to obtain a large per cent, 

 of good membranes and usually the percentage of development 

 from normal insemination is very low. At such times no experi- 

 ments of this nature were performed, but for all other periods 

 in which observations have been made throughout two summers 

 the results have been entirely consistent. 



The following experiment, a typical one, will serve to present 

 the method of treatment and the results obtained from this line 



of study. 



Experiment 23 B. July 19, 1915. 



3:00 P.M. Eggs collected and washed. 



5:00 P.M. Butyric acid exposure (50 c.c. sea water + 2.8 c.c. 

 n/io butyric acid). 



1 That the membranes have been completely shaken off the egg and have not 

 simply collapsed is indicated by the fact that eggs which have been shaken less 

 vigorously than others, still possess pieces of membrane adhering to the surface 

 of the egg; also by the fact that immediately after shaking, no indication of a mem- 

 brane is present, and that shortly a new surface film, the hyaline layer, appears 

 around the egg. 



- The number of cleavages is considerably greater. In a great many eggs the 

 blastomeres fall apart, due to lack of a membrane, and do not reach a swimming 

 stage. 



