8o2 BIOPHYSICAL PHENOMENA [pt. iii 



Hober's erythrocytes, the chief factor producing electrical resistance 

 in eggs was the membrane. This conclusion was supported by various 

 other workers, such as Lyon & Shackell, who reported that salts 

 would enter and leave the fertilised Arbacia Qgg more easily than the 

 unfertilised. Their only exception was iodine, which seemed to show the 

 re\'erse behaviour. Harvey found that eggs became more permeable 

 to sodium hydroxide after fertilisation, and Lyon & Shackell made 

 similar observations with vital dyes. McClendon concluded that there 

 was probably no liberation of electrolytes after fertilisation, but rather 

 an increase of permeability to outside electrolytes. Parthenogenesis 

 gave identical results with fertilisation. 



McClendon's results were in general confirmed by Gray^. In- 

 variably there was a decrease in electrical resistance immediately after 

 fertilisation, as the following figures show: 



Percentage decrease of 

 electrical resistance 

 on fertilisation 

 Echinus acutus ... ... ... ii-2 



Echinus miliaris ... ... ... lo-g 



Echinus esculentus ... ... ... I2"5 



Asterias glacialis ... ... ... 7*4 



Strongylocentrotus lividus ... ... 36-0 



Sphaerechinus granulans ... ... 23-0 



Arbacia pustulosa ... ... ... 15-0 



but half-an-hour or more after fertilisation this decrease was not so 

 apparent. Gray concluded that the entrance of the spermatozoon 

 into the tgg causes an increase in electrical conductivity which 

 attains its maximum within ten minutes, and is followed by a return 

 to the value for the unfertilised G.gg. In later experiments he was 

 unable to confirm this return to the original level, and published 

 curves showing a gradual fall in resistance. Parthenogenesis, he 

 found, did not give quite the same eflfect as normal fertilisation; 

 thus by different methods, Sphaerechinus eggs gave increases of con- 

 ducti\ity of 21-7, 6-8, and 6-o per cent., instead of the normal 23 per 

 cent. Hypertonic sea water markedly increased the conductivity of 

 normal unfertiHsed eggs, the increase actually taking place while the 

 eggs are in the hypertonic solution, but after artificial membrane 

 formation, the conductivity was unaltered by this treatment. Change 

 in the internal pYL of the egg-cells, as found by exposing Arbacia eggs 

 to ammonia solutions and noting the colour change of the pigment 

 inside, produced no alteration in electrical conductivity. To support 



^ But see the criticisms of Cole regarding this (p. 829). 



