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 + 



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 (HC1, HN0 3 , H 2 S0 4 ) 

 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 + 



2 or 3 c.c. of N/10 HC1 and then replaced in normal sea-water. 1 

 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, KC1, CaCl 2 , and 

 MgCl 2 , 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 MgCl 2 and then 



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

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

 zur kiinstlichen Parthenogenese, p. 77, 1906. 



57 



