October 4, 1907] 



SCIENCE 



431 



pressure of the solution, and the other the^ 

 concentration of the hydroxyl ions. It 

 could be shown that these two agencies 

 can with good results be applied sepa- 

 rately, and that therefore there exists a 

 far-reaching analogy between the effects 

 of the alkali in these experiments and the 

 fatty acid in the experiments previously 

 mentioned. If the unfertilized eggs of 

 Strongylocentrotus are first put for two 

 hours into a mixture of 50 c.c. of a neutral 

 van't Hoff solution isotonic with sea- 

 water plus i or 1 c.c. N/10 NaHO and 

 then for from 30 to 50 minutes into hyper- 

 tonic sea-water (50 c.c. sea-water plus 8 c.c. 

 2^N NaCl) many eggs or the majority 

 will develop into larvse. If the eggs are 

 treated with the alkaline solution alone, 

 without being subsequently treated with 

 hypertonic sea-water, they ■will not develop. 

 The treatment of the eggs for from two 

 to three hours with NaOH acts, therefore, 

 in a way similar to the treatment of the 

 same eggs for about two minutes with a 

 solution of the fatty acid of the same con- 

 centration. The analogy shows itself also 

 in that with this method of combining the 

 effects of alkali and hypertonic sea-water 

 those eggs which develop into larvae form 

 often, if not always, a membrane. This 

 membrane is not quite as distinct as the 

 fatty-acid membrane for the reason that it 

 surrounds the cytoplasm more closely. 

 This membrane formation does not occur 

 or does as a rule not become manifest until 

 the eggs are returned from the hypertonic 

 to the normal sea-water. If the order of 

 events is reversed and the eggs are first 

 put into the hypertonic sea-water and 

 afterwards into the hyperalkaline solution, 

 they must remain longer in the hypertonic 

 sea-water, namely, for from 1^ to 2 hours; 

 this also corresponds to the experience 

 with the fatty-acid treatment. 



We therefore possess two parallel 

 methods by which we can imitate the 



fertilizing effects of the spermatozoon upon 

 the egg of Strongylocentrotus, namely, we 

 treat the unfertilized egg for from 1 to 2 

 minutes with a solution of fatty acid (50 

 c.c. M/2 van't Hoff solution plus 0.7 c.c. 

 N/10 butyric acid) or for from 2 to 3 

 hours with an equivalent alkaline solution 

 (50 c.c. M/2 van't Hoff solution plus 0.7 

 c.c. iV/10 NaHO) and afterwards for from 

 30 to 50 minutes with hypertonic sea-water 

 (temperature = 15° C). The treatment 

 of the eggs with fatty acid or alkali can be 

 replaced by a treatment with a fat solvent. 

 Fatty acids, alkalis and fat solvents all 

 act in the same way, namely, by causing 

 those changes in the egg which result in the 

 process of a membrane formation. 



IV 



I have not yet had time to apply these 

 results to the eggs of many other forms, 

 but I believe from what I have seen that 

 we are now in possession of at least some of 

 the general methods and principles of arti- 

 ficial parthenogenesis. It seems that in 

 general the treatment of the eggs with 

 alkalis and acids, sometimes with, some- 

 times without subsequent treatment with 

 hypertonic sea water, causes the develop- 

 ment of unfertilized eggs. 



The unfertilized eggs of Polynoe, a 

 marine annelid, can develop into larva if 

 they are permanently put into hyperalka- 

 line sea-water, e. g., 50 c.c. sea-water plus 

 1.5 c.c. n/10 NaHO. It is well to keep the 

 eggs for this experiment in shallow watch- 

 glasses which are loosely covered with 

 glass plates ; in this case the oxygen of the 

 air diffuses more readily to the eggs, than 

 if they are kept in dishes with a deep layer 

 of liquid above them. These eggs of 

 Polynoe are immature when taken from the 

 ovary and do not become mature in ordi- 

 nary sea-water unless they are fertilized 

 by a spermatozoon. They become, how- 

 over, mature without the aid of sperm, 



