INFLUENCE OF HYDROGEN ION CONCENTRATION. 315 



sea water, maturation proceeds only as far as the formation of the 

 first maturation spindle. Unless the egg is fertilized or arti- 

 ficially stimulated it remains in the metaphase of the first matura- 

 tion division. After fertilization the maturation divisions are 

 completed and the polar bodies are formed at the animal pole. 

 Mead (8) first called attention to the fact that a small amount of 

 KC1 added to sea water causes these eggs to complete the matura- 

 tion process with polar body extrusion, an event in this case sig- 

 nifying initiation of development. Three years later Loeb (9), 

 having succeeded in obtaining parthenogenetic development of 

 echinoderm eggs by the use of hypertonic sea water, tried similar 

 procedures on Chcetopterus eggs. He also examined the influence 

 of KC1 and concluded that activation in this case was not a con- 

 sequence of increase in osmotic pressure, but a specific effect o j " 

 K-ions. In a careful description of the parthenogenetic develop- 

 ment of this egg, he pointed out that after treatment with KG, 

 development and differentiation appear to proceed without cell 

 cleavage (an observation subsequently confirmed by F. Lillie, 10), 

 and that activation of the egg is accompanied by marked ame- 

 boid movements of the protoplasm. He did not succeed at this 

 time in obtaining development with cleavage, though later in col- 

 laboration with Wasteneys he obtained cleavage by the combined 

 use of SrCL and ox serum. Loeb also decribed a marked ten- 

 dency in Chcetopterus eggs activated by KC1 to adhere to each 

 other; as a result of this adhesion, larvae might be formed con- 

 sisting of several swimmers partially fused, or in some instances, 

 of giant swimmers resulting from the complete fusion of several 



eggs. 



Loeb also obtained ciliated, unsegmented larvae by treating 

 Chcetopterus eggs with 100 cc. sea water -\- 2 cc. iV/io KOH, and 

 with 100 cc. sea water -f- 2 cc. iV/io HC1. He mentions the fact 

 of activation by HC1 as striking since he had failed to get activa- 

 tion of echinoderm eggs by similar treatment. (It was not 

 until five years later that he tried the fatty acids with signal 

 success.) Allyn (n) has recently examined the action of sev- 

 eral acids on Chcetopterus eggs. She failed to get segmentation 

 and concluded that acids are less effective than KC1. 



In our experiments with Chatoptcrus we have observed the 



