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 sipunculid— 
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 limpid 
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 
1 Loeb, ‘‘ Ueber die Hervorrufung der Membranbildung beim Seeigelei durch 
das Blut gewisser Wiirmer (Sipunculiden),’’ Pfliiger’s Archiv, CXVIII, 36, 1907; 
“Ueber die Hervorrufung der Membranbildung und Entwicklung beim Seeigelei 
durch das Blutserum des Kaninchens,’’ Pfliiger’s Archiv, CX XII, 196, 1908; 
‘“‘Weitere Versuche ueber die Entwicklungserregung des Seeigeleies durch das 
Blutserum von Siugetieren,’’ Pfliiger’s Archiv, CX XIV, 37, 1908. 
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