Hisrory oF ARTIFICIAL PARTHENOGENESIS 
Or 
Or 
order to see whether it were not possible to cause unfertilized 
sea-urchin eggs to develop into larvae by altering the constitu- 
tion of the sea-water. My chief idea was that it must take 
place by means of hydroxyvlions or of hydrions. For earlier 
experiments had shown that an addition of acid to sea-water 
retards the development of sea-urchin eggs.! 
Moreover, it was conceivable that the alkali of the sea- 
water or the formation of carbonic acid in the unfertilized eggs 
was itself the cause that they began occasionally to divide 
spontaneously after a prolonged sojourn in sea-water. So I 
then tried whether it was possible to cause the development 
of the unfertilized sea-urchin egg into a larva by means of alka- 
lies or acids.2 My later investigations have shown that I 
was right in this idea, but through a curious accessory circum- 
stance I did not at that time succeed in my object. For I 
was then of the opinion that only the hydrions are of impor- 
tance in the physiological effect of acid, and hence I used only 
strong mineral acids. I have since found that in this case only 
the weak acids are effective. Had I used fatty instead of 
mineral acids, the development of this branch of biology would 
have been shortened by five years. 
On the other hand the experiments on the addition of MgCl, 
to the sea-water were successful, provided that at the same 
time the osmotic pressure of the sea-water was raised.* Untferti- 
lized sea-urchin eggs which had been exposed for two hours to 
such a mixture developed afterward into larvae, some of which 
reached the normal pluteus stage. In this way the first step 
was taken which rendered possible the systematic analysis of 
the nature of the process of fertilization. For we possess only 
1 Loeb, ‘“‘Ueber den Einfluss von Siuren und Alkalien auf die embryonale 
Entwicklung und das Wachstum,”’ Archiv f. Entwicklungsmechanik, VII, 631, 1898. 
2 Loeb, Am. Jour. -Physiol., III, 434, 1900. 
3 Loeb, ‘‘On the Nature of the Process of Fertilization, and the Production 
of Normal Larvae (Plutei) from the Unfertilized Eggs of the Sea-Urchin,’”’ Am. 
Jour. Physiol., III, 135, 1899. 
