222 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 
Naples by treating their eggs with hypertonic sea-water.' 
He also investigated the effect of acids. 
Hydrochloric acid has been found by Loeb to be an efficient 
reagent for causing artificial parthenogenesis in starfish. He found it 
did not succeed in Arbacia punctulata (at Woods Hole). Butstrangely 
enough it is one of the best reagents I found for Arbacia pustulata 
(at Naples). Usually 2, 3, 4, 5, 6, and 7c.c. of a N/10 solution of 
hydrochloric acid in sea-water was added respectively to dishes 
containing 100 c.c. of sea-water. Eggs immersed in these solutions 
were taken out at intervals of from two to fifteen minutes. Some of the 
best results were obtained from 2 c.c. acid in 100 c.c. sea-water, ten to 
fifteen minutes’ exposure; 3 c.c. acid, seven to twelve minutes’ 
exposure; 4 ¢.c. acid, nine minutes’ exposure; 7 c.c. acid, five minutes’ 
exposure. .... In the best experiments perhaps 10 per cent of the 
eggs developed into swimming larvae. Many of these swam up to 
the top of the liquid, just like the larvae from fertilized eggs. They 
formed fully developed plutei which lived as long as individuals pro- 
duced from fertilized eggs and kept under the same conditions. 
No positive results were, however, obtained by this method 
at Naples with S. lividus, but Lyon succeeded in obtaining a 
couple of larvae by treating the unfertilized eggs of S. lividus 
with carbonic acid in sea-water. The importance of membrane 
formation from the point of view of development was not recog- 
nized at that time, but I believe that the eggs in Lyon’s experi- 
ment formed a gelatinous membrane. 
We may as well point out here that the eggs of S. purpuratus 
and franciscanus at Pacific Grove cannot be made to develop 
into larvae by a mere treatment with acid unless they are kept 
at a very low temperature. In this respect, there is a quali- 
tative difference between the eggs of the European and Cali- 
fornian sea-urchins. 
This difference between the behavior of the eggs of 
Strongylocentrotus at Naples and in California is also corrobo- 
1K. P. Lyon, ‘‘Experiments in Artificial Parthenogenesis,’’ Am. Jour. 
Physiol., IX, 308, 1903. 
