THE RHYTHM OF IMMUNITY AND SUSCEPTIBILITY 



OF FERTILIZED SEA-URCHIN EGGS TO ETHER, 



TO HC1, AND TO SOME SALTS. 



E. G. Sl'AULDING. 



INTRODUCTION. 



The experiments described in this paper were undertaken 

 during the summer of 1902 at the Marine Biological Laboratory 

 upon the suggestion of Dr. A. P. Mathevvs ; their publication has 

 been delayed because of the pressure of other work and of the 

 desire to, if possible, get beyond their mere description to their 

 meaning. This end is believed to have been attained in connec- 

 tion with the working out of a synthesis of the artificial parthen- 

 ogenetic methods, the detailed results of which attempt appear in 

 a preceding paper. 1 The effectiveness of all these methods and so 

 the special physico-chemical result of normal fertilization and the 

 nature of cleavage processes can, it is believed, be explained from 

 a unitary standpoint, viz.: if it is considered that in the process of 

 cleavage an average decrease in surface tension takes place as a 

 result of the equilibrating of a potential difference between os- 

 motic pressure and surface tension, accompanied by such elec- 

 trolytic changes as cause the constricted form. That this average 

 decrease in surface tension takes place is a necessary inference 

 from the change from the approximately spherical to the con- 

 stricted form of the egg at cleavage, for this means an increase 

 in surface. It carries with it, therefore, the decrease in that po- 

 tential, osmotic, which opposes surface tension in direction. The 

 preceding cause in these events is the creation of a potential dif- 

 ference by first increasing the osmotic pressure, which is done 

 artificially by each of the parthenogenetic methods. Accor- 

 dingly with the equalization of this difference, caused, c. g., by a 

 splitting up of colloidal particles or molecules, there is in the case 

 of eggs of marine forms an absorption of water. Both of these 



1 Spaulding, E. G. " The special physics of segmentation as shown by the syn- 

 thesis, from the standpoint of universally valid dynamic principles, of all the artificial 

 parthenogenetic methods." BIOLOGICAL BULLETIN, February, 1904. 



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