130 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 
is, however, 0.94 m, or isosmotic with sea-water. But this 
solution acts just as hypertonically upon the sea-urchin egg asa 
0.80 m NaCl solution, i.e., a solution whose osmotic pressure 
is: about 50 per cent higher than that of a 0.94 m cane-sugar 
solution. 
It can be directly shown that a solution of cane sugar, 
which is theoretically isosmotie with sea-water, is actually 
hypertonic for the sea-urchin egg. For the eggs shrivel in such 
a solution; they even shrink ina7/8m cane-sugar solution; in a 
6/8 m solution they retain their volume and in a 5/8 m solu- 
tion they increase in size. Eight years ago I also observed that 
medusae (Polyorchis) shrink considerably in a pure cane-sugar 
solution that is theoretically isosmotic with sea-water. 
It can be indirectly shown that a 3/4 m cane-sugar solution 
is about the concentration that is isotonic for the sea-urchin 
egg, by placing sea-urchin eggs that have been fertilized with 
sperm in pure cane-sugar solutions of different concentrations 
immediately after fertilization. Experiments of this description 
showed that in a 6/8 m cane-sugar solution the first cell division 
occurs in all the eggs of purpuratus, and indeed at almost thesame 
time as in normal sea-water; while in 5/8 and 7/8 m solutions its 
onset is delayed and occurs in only a few eggs. In cane-sugar 
solutions below 5/8 m and above 7/8 m as a rule not a single 
egg divided. In 6/8 m cane-sugar solution, again, the cleavage 
did not go beyond the four- or eight-cell stage, which is in 
accordance with the experience in muscle. But if the eggs are 
replaced in sea-water they develop normally. This behavior 
of the egg in a cane-sugar solution corresponds to the behavior 
of a medusa in the same solution: for in the latter, also, as well 
as in the heart; the spontaneous contractions cease in a pure 
cane-sugar solution.! These observations have a bearing upon 
a controversy between Delage and the writer. Delage used in 
his experiments on artificial parthenogenesis cane-sugar solu- 
1 Loeb, Am. Jour. Physiol., III, 384, 1900. 
