DEVELOPMENT WITHOUT MEMBRANE FORMATION 221 
also with a mixture of sea-water and pig’s serum without 
the addition of SrCl,.' But at this time the writer was not 
yet familiar with the gelatinous form of membranes in the 
eggs of this species, and so he must leave it in doubt whether 
or not gelatinous membranes were formed in the eggs which 
developed. 
The following hitherto unpublished experiments are rather 
curious. Unfertilized eggs (without membranes) were placed 
in m/2 sodium butyrate solution and taken out from it at differ- 
ent intervals. The solution was strongly alkaline (requiring 
4.2c.c. N/10 HCl [per 50 ¢.c. of solution] to turn neutral red 
from yellow to red). 
A large number of the eggs formed membranes, but most of 
these (if not all) succumbed to cytolysis. However, a small 
number (about 1 per cent) of the eggs removed after between 
three and four hours developed into swimming larvae. These 
eggs possessed either no membrane or only one that adhered 
very closely to the egg, probably a gelatinous membrane. The 
experiment was repeated with a sodium butyrate solution of 
much diminished alkalinity. The amount of cytolysis (and 
membrane formation) was reduced by this, but the activation 
of a few eggs took place in this case also (but not, of course, 
before the eggs had been transferred to normal sea-water). 
About 2 per cent of the eggs that had been about six or seven 
hours in the sodium butyrate solution developed into swimming 
larvae. I believe that in both these cases a gelatinous mem- 
brane was formed, but the remarkable fact is that the eggs 
developed to the blastula stage at room temperature without 
subsequent treatment with a hypertonic solution. Could it be 
possible that the butyrate solution acted like a solution in 
which oxidations were prevented ? 
3. E. P. Lyon succeeded in causing artificial partheno- 
genesis in Arbacia pustulata and Strongylocentrotus lividus at 
1 Loeb, Pfliiger’s Archiv, CX XIV, 50, 1908. 
