770 STUDIES. IN GENERAL 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, Cheetopterus, 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 Chetopterus, 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 larve 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 can be made to develop into 
larvee by squirting them from one vessel into another by 
means of a pipette. This does not succeed with every culture, 
but still very frequently.’ 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] suspect that the skaking affects the development of the egg only in an indrect 
way. [1903] 
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