EXPERIMENTS ON ARTIFIOIAL PARTHENOGENESIS 769 
is sufficient to obtain larve.' Eggs as sensitive as this must 
be carefully handled in two directions if one does not wish 
to obtain deceptive results. First it is necessary to transfer 
the eggs from one dish to another in such a way that every 
mechanical agitation is done away with. This is best done 
by using pipettes with a wide opening for sucking up and 
transferring the eggs. The latter manipulations must then 
be made with the greatest care. The second precaution 
consists in this, that whenever the experimental eggs are 
transferred from one solution to another or into sea-water the 
same mechanical manipulation must be repeated in exactly 
the same way with the control eggs. In this way it can 
be determined whether the parthenogenetic development in 
individual cases is attributable to mechanical agitation, or to 
other agents which one employs. With these precautions we 
have made a series of experiments this summer on Asterias 
eggs and have found up to the present time that, independ- 
ently of mechanical agitation, only two methods lead to 
artificial parthenogenesis in starfish eggs. First, the intro- 
duction of the eggs for from three to twenty minutes into 
sea-water to which 3 to 5 c.c. of a 34 normal HCl or some 
other inorganic acid has been added to each 100 c.c. of sea- 
water. The second method which was discovered by my 
pupil, Mr. A. W. Greeley, consists in keeping the eggs, after 
lying for a certain time in sea-water, on ice for a number of 
hours. Other methods all gave negative results, especially 
heating the eggs which Mr. Greeley also tried. Neither did 
we succeed in obtaining clear results through the abstraction 
of water from the egg, so that I suspect that in my earlier 
experiments perhaps, in which I found starfish eggs to 
develop through an increase in the concentration of the sea- 
water, mechanical agitation really caused the development. 
1I have since found that the eggs of the starfish can develop without any notice- 
able external cause. [1903] 
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