186 



Dr. A. D. Waller. On the 



[July 17, 



and 3 were used in the absence of incubation for a careful examination 

 of the exposed blastoderms, one at normal temperature, the other at 

 38° ; polarisation currents were alone observable in these two cases, 

 amounting to ± 0*0002 volt. Nos. 4, 5, and 6 at 50 and 58 hours 

 gave positive blaze of only 0*0030 and 0*0010 volt, and their blasto- 

 derms were found to be very defective. Nos. 6, 7, 8, 9, and 10 gave no 

 blaze whatever, only the usual small counter-deflections of ± 0*0002 

 volt due to polarisation, and on being opened exhibited no sign of 

 development. 



Incidentally to this first series of trials I noted that : — 

 1. The " normal current," from a developing egg, led oft' as described, 

 is positive or ascending, and if the egg is left undisturbed diminishes 

 during observation. I consider it to be a " manipulation blaze " 

 due to handling of the egg and disturbance of the embryo. It is 

 presumably the current first pointed out by Hermann and von Gendre 

 in their statement that the embryo is positive to any other part of 

 the egg contents, i.e., that there is a current from content to 

 embryo.* 



Fig. 1. 



30 mins. 



Hen's Egg after 48 hours' incubation. Coil at 0. Single break shocks in ascend- 

 ing ( + ) and descending ( — ) directions. Response only in ascending ( + ) 

 direction. 



2. The embryo is easily exhausted and killed by repeated excitations 

 of moderate and of excessive strength. Fig. 1 (No. 1935) exhibits 

 the fatigue decline of a succession of reactions to strong induction 



* Hermann u. ron G-endre, " Ueber eine Electromotorische Eigenschaft des 

 bebruten Huhnereies," ' Pfluger's Archir,' 1885. 



