ORIGINAL METHOD OF ARTIFICIAL PARTHENOGENESIS 165 
2.0 c.c. N/10 NaOH, 0, 2, 4, 8, and 16 c.c. of 24 m KCl were 
added. Unfertilized eggs were divided among these five solu- 
tions and portions of the eggs transferred to norma! sea-water 
after 45, 64, 89, 116, and 144 minutes. The results are sum- 
marized in Table XXXIII. The increase of osmotic pressure 
is given in the table in round numbers as a percentage of the 
pressure of the half grammolecular solution. 
TABLE XXXIII 
INCREASE OF THE OSMOTIC PRESSURE OF THE SOLUTION 
TIME OF 
EXPOSURE | | 
oO Per Cent)16 Per Cent 30 Per Cent 55 Per Cent | 87 Per Cent 
zen oS Ae eas WR etinceeeeetl (Res Ste eee Set Bir Ia | Se 
45 minutes... .| 0 0 | 0 0 numerous 
| larvae 
64 minutes.... 0 0 0 mMuUumMerousit es. Seo 
larvae 
89 minutes.... 0 0 EMUMerOUSs |store ae ole eee 
larvae | 
116 minutes.... 0 (eee eer ees oe | Be chal yee eee 
144 minutes.... 0 (Jie | tee: ee | BE AN | Pucca Nee 
' 
Further experiments on the eggs of S. purpuratus showed 
that tbe results remain the same if the two agencies, the base 
and tbe neutral hypertonic solution, are applied in succession 
instead of simultaneously. When the treatment of these eggs 
with the alkaline solution (added to a neutral isotonic solution) 
preceded their treatment with a neutral hypertonic solution, 
it could be seen that the former agency acted mainly as the 
membrane-forming agency, while the hypertonic solution acted 
as the corrective agency. 
For the egg of Arbacia a neutral hypertonic solution suffices 
to call forth a normal development. 
3. Why should the addition of alkali to the hypertonic 
solution increase its efficiency? The answer is that the ad- 
dition of alkali increases the membrane-forming effect of the 
hypertonic solution. In S. purpuratus the hypertonic solution 
