ARTIFICIAL PRoDUCTION oF NorMAL Larvae 621 
and were fertilized afterward rose to the surface. Even 
this difference might be caused to disappear by further 
experimentation. 
An agency which causes the egg to go through only the 
first stages of segmentation, which lead, for instance, to a 
division of the egg into 2, 4, or 8 cells, need not necessarily 
have much in common with those agencies in the sperma- 
tozoon that cause the development of the fertilized egg. But 
if the egg can be caused through an artificial influence to 
reach the blastula stage and swim about, the artificial cause 
must have more in common with the effective element in 
the spermatozoon. If however the artificial influences cause 
the egg to reach the pluteus stage, or in other words cause 
the egg to develop as far as the fertilized egg can be 
developed at present in our laboratory, I think the two pro- 
cesses of artificial and natural development must be pretty 
closely allied. 
It is in harmony with our statement that a very large 
number of conditions cause an unfertilized egg to reach a 
two- or four-cell stage. It suffices to leave the eggs for some 
time in sea-water (about twenty-four hours). A slight 
increase in the alkalinity of the sea-water causes the begin- 
ning of a segmentation much sooner. A short treatment 
with sea-water that is faintly acid has the same effect. An 
increase in the concentration of the sea-water which probably 
causes a loss of water in the egg has the same effect (Morgan). 
Morgan found more recently that treatment with a solution 
of strychnia salts may lead to a beginning of segmentation.’ 
Possibly in this case the alkalinity of the sea-water was 
modified. But none of these or the other methods mentioned 
above has yielded blastule, gastrulz, or plutei. 
There is at present only one way known by which the 
1MorGAN, Science, Vol. XI (1900), N. S., p.176. R. Hertwig had found this many 
years ago. 
Digitized by Microsoft® 
