VII 



THE FIRST EXPERIMENTS UPON THE OSMOTIC ACTIVA- 

 TION OF THE UNFERTILIZED EGG OF THE 

 SEA-URCHIN (Arbacia) 



1. As already mentioned, I began my investigations with 

 the anticipation that it must be possible to induce the un- 

 fertilized eggs to develop by treating them with bases or acids. 

 For several weeks in the summer of 1899 I conducted experi- 

 ments in this direction on the eggs of a sea-urchin, Arbacia, 

 at Woods Hole, without obtaining any other result than that 

 the unfertilized eggs of Arbacia placed in 100 c.c. of sea-water-f 



1 c.c. of N/10 NaOH begin to segment after remaining in the 

 solution for about five hours. The cleavage, however, was very 

 irregular and did not go beyond the early stages — two or four 

 cells. At the same time the eggs showed a tendency to become 

 amoeboid. The experiments with acids (HCl, HNO3, H2SO4) 

 showed that no cleavage took place in acidified sea-water, but 

 that a few divisions might be observed in unfertilized eggs if 

 they were placed for about ten minutes in 100 c.c. of sea-water -f- 



2 or 3 c.c. of N/10 HCl and then replaced in normal sea-water.' 

 Experiments with salt solutions which were isosmotic with 

 sea-water gave no better results. When the summer of 1899 

 had almost entirely elapsed in this manner without any 

 success, I at last investigated the effects of hypertonic solutions. 

 10/8 m (grammolecular) solutions of NaCl, KCl, CaCla, and 

 MgCla, were prepared and mixed in different proportions 

 with sea-water. After prolonged experiments I found that if 

 unfertilized sea-urchin eggs were exposed for two, hours to a 

 mixture of 50 c.c. of sea-water+50 c.c. 10/8 m MgCl2 and then 



' Loeb, "On the Artificial Production of Normal Larvae from the Unfertilized 

 Eggs of the Sea-Urchin," Am. Jour. Physiol., Ill, 434, 1900; Untersuchungen 

 zur kUnstlichen Parthenogenese, p. 77, 1906. 



57 



