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3. ELECTRICITY AND MAGNETISM 



An external agent, to which all eggs are inevitably exposed, is 

 the natural magnetism of the earth. No evidence has, however, 

 as yet been brought forward that this agent exercises any directive 

 influence upon them, although their development may be distorted 

 by excessive exposure to it. 



Thus Windle placed a number of Hens' eggs between the 

 poles of a large horse-shoe magnet. Over 50 % of these, when 

 incubated, gave rise to abnormalities, the area vasculosa being 

 affected in most cases. No relation could be detected between 

 the position of the egg in the magnetic field and the kind of 

 monstrosity produced. 



In the case of Trout ova similarly treated a very high death- 

 rate was observed, but this was attributed by the experimenter 

 to the action of the electric currents set up by the running water 

 between the poles of the magnet. Weak electric currents had 

 less effect. 



Silkworms' eggs, however, suffered no harm. 



The effects of the electric current upon the eggs of Amphibia 

 and Birds were tested by some of the older observers. Rusconi, 

 Lombardini, and Fasola all found that the development of the 

 Frog's egg could be accelerated by weak currents. Lombardini 

 produced monstrosities in the case of the Chick by this method. 

 More modern experiments are due to Windle, Dareste, Rossi, 

 and Roux. 



Windle observed a fairly high death-rate amongst Trout eggs 

 exposed to the action of the current. Dareste has found a large 

 percentage of monsters among embryos developed from Hens' 

 eggs subjected for from one to three minutes to the electric 

 spark (12 cm. long from Bonnetty's machine, 3-35 cm. long 

 from a Rhumkorff coil). Development was, however, normal in 

 the case of eggs placed for an hour in a Tesla's solenoid traversed 

 by a discharge of 500,000 periods a second. Rossi employed 

 a continuous current passing through the eggs (of Salamandrina 

 perspiciUata) in the direction of the axis. Both yolk and 

 pigment became aggregated at the animal pole, leading to the 

 formation there of a grey raised area surrounded more or less 



