MARY GRACE SPRINGER. 



at least by the fact that toward the end of the breeding season 

 the physiological condition of the eggs was far from uniform. 

 In general it was found that the starfish cultures containing ex- 

 tract showed a slight retardation, a higher degree of cytolysis, 

 and a greater tendency to stop either at the blastula or the gastrula 

 stage. 



All the extracts used in these investigations upon Asterias eggs 

 were made in a solution of sea water. 



THE EFFECTS OF EMBRYOLOGICAL EXTRACTS ON THE EARLY 

 STAGES OF THE SEA-URCHIN EGG. 



The following experiments were all performed on the sea- 

 urchin, Arbacia pnnctulata, to find out if the extracts of various 

 larval stages have any effect on developing eggs of the same 

 species. The eggs of Arbacia while more stable, and therefore 

 less desirable than those of Asterias, can be obtained in convenient 

 quantities for use in making extracts. 



About sixty series of experiments were performed. The 

 method was strictly comparative. It will be noted that the tables 

 show, not only the effect of a given extract, but its effect in vary- 

 ing concentrations as well. 



Particular emphasis is laid on the fact that the experiments 

 given in outline in the table are type experiments. Each experi- 

 ment outlined is one of several very similar experiments unless 

 otherwise stated and is taken as fairly representative of the results 

 obtained in all the experiments of that series, the others of 

 which are omitted to avoid unnecessary and tedious repetition. 



Series 15. 

 TABLE I. 



