AKTIFICIAL PKODUCTION or NORMAL LARV.E 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. 1 

 Possibly in this case the alkalinity of the sea-water was 

 modified. But none of these or the other methods mentioned 

 above has yielded blastulse, gastrulae, or plutei. 



There is at present only one way known by which the 



i MORGAN, Science, Vol. XI (1900), N. S., p. 176. R. Hertwig had found this many 

 years ago. 



