798 BIOPHYSICAL PHENOMENA [pt. m 



found the horny cases to be quite permeable to salt, by simple osmo- 

 meter measurements (see also p. 331 in the section on Constitution). 

 Jacobsen & Johansen made similar observations, finding that the 

 A and salinity of plaice eggs varied somewhat with the environ- 

 ment, but was always much lower than that of sea water. Death 

 permits the entrance of salt, and the eggs sink to the bottom. Certain 

 observations have also been made on the adaptation of fish eggs to 

 different saHnities; thus Amemiya found that the eggs of the ana- 

 dromus "Ayu" fish, Plecoglossus altivelis, will not hatch in water of 

 salinity above 20 per cent., 22 per cent, is very quickly lethal, and 

 15 per cent, optimum. 



Osmotic pressure experiments with the eggs of Fundulus were done 

 by Loeb & Cattell and by Loeb & Wasteneys. They studied the 

 various antagonistic effects which electrolytes display on the stoppage 

 of the heart-beat of the embryo. Embryos cannot recover from 

 potassium chloride poisoning without the aid of other electrolytes, 

 so Loeb & Cattell studied the efficiency of the different anions and 

 cations. Loeb & Wasteneys concluded that the egg-membrane of 

 Fundulus is almost impermeable to water and salt under normal 

 conditions. 



Fragmentary results on other fish eggs have been obtained by 

 Ziegelmayer, who tested the effects of hormones and of various 

 other substances on the size of Leuciscus eggs. 



McClendon found, with Loeb & Wasteneys, that the egg-mem- 

 branes of Fundulus were practically impermeable, and showed that, 

 when by poisons this impermeability had been abolished, abnor- 

 malities occurred. Later, McClendon observed that the action of 

 various toxic solutions markedly increased the permeability of the 

 membranes to salts, but that their action was inhibited to some 

 extent by anaesthetics. This last effect was confirmed in detail with 

 the eggs of the pike, Esox. Anaesthetics that retarded development 

 (2 to 3 per cent, alcohol or 0-5 per cent, ether) tended to inhibit the 

 permeability-increasing action of a i/io molecular solution of sodium 

 nitrate. Osterhout showed in 19 14 that plant cells were made more 

 permeable with increase of temperature, and McClendon extended 

 this finding to the eggs of Esox, which is interesting in view of 

 Ephrussi's results on echinoderm eggs (see p. 806). Loeb used the 

 egg-membranes of Fundulus in many experiments on ionic per- 

 meability, e.g. specific gravity tests 



