ACTIVATION OF UNFERTILIZED STARFISH EGGS. 101 



elements for one to two minutes; l but the conditions (nature of 

 electrodes, distance apart, quantity of sea-water, etc.) are not 

 described. He does not consider the possibility that acid or 

 alkali electrolytically produced, or heat, rather than the electric 

 current as such, may have been responsible for the effect; and in 

 the light of our own experiments it seems highly probable that 

 this was the case. Schiicking found induction shocks to be 

 ineffective, and we have repeated and confirmed this observation. 

 In the condenser-like arrangement used by Delage, 2 the actual 

 physical conditions were ill-defined. Delage's aim was to affect 

 the eggs electrostatically (by induction); they were placed in a 

 layer of sea-water separated by a thin sheet of mica from a sheet 

 of tinfoil, the sea-water and the metal being connected with the 

 poles of a battery. His results were irregular, and he himself 

 expresses doubt as to the real nature of the conditions. The 

 presence of currents and of products of electrolysis seems not to 

 have been excluded. 



In the eggs of amphibia McClendon was able to start cleavage 

 and development by passing the alternating current from the 

 lighting circuit (no volts, 60 cycles) through the water containing 

 the eggs. 3 In this case a current of considerable intensity acted 

 for a brief period (i to 2 seconds), and the effect was probably not 

 caused by electrolytic products or heat. Further and more 

 precise investigation of the conditions of electrical partheno- 

 genesis in these eggs seems desirable. 



Our aim in the experiments described in this paper has been (i) 

 to ascertain whether in fact activation of starfish eggs by the 

 direct electric current is possible, and to what degree, and (2) to 

 determine more precisely the conditions, more particularly of 

 current intensity, time of exposure and temperature, under which 

 the effect is produced. The experiments were performed on the 

 unfertilized eggs of As^erias forbesii at Woods Hole during the 

 summers of 1922 and 1923. The direct current was used in all 

 cases. Usually the eggs were exposed to the current during the 

 interval between the breakdown of the germinal vesicle and the 

 separation of the first polar body (prematuration period) ; 4 for 



1 Schiicking, A., Arch. ges. Physiol., 1903, XCVIL, 86. 



- Delage, Y., Arch. zool. exper. et gen., Ser. 4, 1908, IX., p. xxx. 



3 McClendon, J. F., Amer. Jour. Physiol., 1912, XXIX., p. 299. 



4 The period most favorable for fertilization and artificial activation. 



