770 STUDIES IN GENEKAL PHYSIOLOGY 



I believe also that Delage has in part been led into error by 

 this circumstance when he asserts that about every physical 

 and chemical factor brings about artificial parthenogenesis. 

 I do not believe that such an assertion could be made on the 

 basis of experiments on sea-urchin eggs. In sea-urchin 

 eggs agitation does not act this way and this source of error 

 which is so inconvenient in working with starfish eggs does 

 not exist here. Nevertheless, I made it a rule from the 

 first to expose the control eggs to the same mechanical agita- 

 tion in the experiments with sea-urchin eggs as the experi- 

 mental eggs themselves. 



3. The precautions necessary for the experiments on star- 

 fish eggs must also be used in the experiments on the eggs 

 of Annelids, Chsetopterus, and Amphitrite. In both these 

 forms it has been possible this summer to bring about arti- 

 ficial parthenogenesis through shaking and mechanical agi- 

 tation of the eggs. In Chsetopterus, however, this result is 

 less certain than in Amphitrite. If the unfertilized eggs of 

 Annelids are allowed to remain in ordinary sea-water without 

 jarring the vessel, the eggs do not develop into larvae any 

 more than do starfish eggs. We cannot speak of a "natural" 

 parthenogenesis of these forms. If, however, they are 

 allowed to remain for thirty minutes in the sea-water the 

 unfertilized eggs of Amphitrite canbe made to develop into 

 larvae by squirting them from one vessel into another by 

 means of a pipette. This does not succeed with every culture, 

 but still very frequently. 1 It is possible, however, to cause 

 the unfertilized eggs of Amphitrite to develop every time 

 without agitation, when they are introduced into sea- water to 

 which a small but definite amount of a soluble calcium salt 

 has been added. It is not necessary to return the Amphi- 

 trite eggs from such a solution to sea-water. They develop 



1 1 suspect that the skaking affects the development of the egg only in an indirect 

 way. [1903J 



