XVIII 



THE FERTILIZING EFFECT OF FOREIGN BLOOD AND 

 FOREIGN CELL EXTRACTS 



1. The following chapter contains, perhaps, the most sur- 

 prising facts in the field of artificial parthenogenesis. The 

 writer succeeded in 1907 and 1908 in showing that the blood and 

 tissue extracts of many foreign species will cause the unfertilized 

 egg of the sea-urchin (and other forms) to form a fertilization 

 membrane (and develop if subsequently treated with a hyper- 

 tonic solution), while the blood and tissue - extracts of their 

 own species have no such effect.^ The first observation on the 

 fertilizing effect of foreign blood was made by the writer in 

 1907 when he succeeded in causing membrane formation in 

 unfertilized sea-urchin eggs with the blood serum of certain 

 worms, the Gephyrea. These eggs also developed. 



By making an incision into the body of a sipuncuUd — 

 Dendrostoma was the form chiefly used — the fluid of the body 

 cavity can be obtained. This fluid contains numerous blood 

 corpuscles and reproductive cells, spermatozoa or eggs. In 

 our experiments we used as a rule only the body-contents of 

 female worms. One c.c. of this fluid was generally diluted with 

 some 50 to 200 c.c. of sea-water. The solution was then com- 

 pletely cleared by centrifuging, and only the perfectly hmpid 

 serum, free from all solid and formed constituents, was used in 

 our experiments. If, now, the unfertilized eggs of a female (sea- 

 urchin) were put in a watch glass with about 3 c.c. of sea-water, 

 and 1 to 4 drops of this diluted transparent body-cavity fluid 



iLoeb, "Ueber die Hervorrufuug der Membranbildung belm Seeigelei durch 

 das Blut gewisser Wurmer (Sipunculiden)," Pflilser's Archiv, CXVIII, 36, 1907; 

 "Ueber die Hervorrutung der Membranbildiing und Entwicklung beim Seeigelei 

 durch das Blutserum des Kauiachens," PflUger's Archiv, CXXII, 196, 1908; 

 "Weitere Versuciie ueber die Entwickiuugsorregung des Seeigeleies durch das 

 Blutserum von Saugetieren," Pft-ager's Archiv, CXXIV, 37, 1908. 



191 



