8i2 BIOPHYSICAL PHENOMENA [pt. m 



optimum is at 0-956 mol. per litre. Mortality also shows a bell- 

 shaped curve, with an optimum at 1-024. Faure-Fremiet concluded 

 that as the Boyle-Mariotte law j&F = K holds for the egg of Sabellaria 

 alveolata, the method of calculation of Vies & Dragoiu is not 

 applicable to it. He noted finally that, at external osmotic pres- 

 sures which greatly slowed down the speed of development, the 

 ABC 



1-41- 



F 



A, 1st polar body. 

 D, Stage II. 



Fig. 196. 



B, 2nd polar body. 

 E, Stage IV. 



C, Cordiform stage. 

 F, Stage VI. 



processes of division, etc., were not appreciably modified. In another 

 work he stated that the outer egg-membranes of Ascaris were 

 absolutely impermeable, the surface of the tgg cytoplasm only 

 permeable to water, and that the egg-contents was isotonic with a 

 0-7 per cent, sodium chloride solution. 



5*6. The Osmotic Pressure of Terrestrial Eggs 



The eggs of terrestrial animals have not received as much attention 

 from this point of view as have those of aquatic animals. A little 

 work has, however, been done on the silkworm embryo. Polimanti 

 in 1915 and Pigorini, Tonon, Tona & de Ziller in 1927 obtained the 

 following figures : 



Ovarian eggs 



Newly laid eggs (yellow) ... 



After 2 or 3 days (ash-yellow) 



After 3 br 4 days (quite ash-coloured) 



After some months, i.e. in the torpid state 



Caterpillar newly hatched 



Adult imago 



Polimanti 



A(°) 



-0-650 

 -o-66o 

 -o-68o 

 -0-690 

 -0-665 

 -0-750 



Pigorini et al. 

 A(°) 

 -0-630 

 -0-580 

 -0-700 

 -0-700 



