230 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 
5. F. Lillie’ has made some interesting experiments on the 
fertilization of the egg of Nereis, an annelid. It seems that 
in this egg the spermatozoon comes in contact with the fertiliza- 
tion cone of the egg and lingers here for more than half an 
hour before it enters. The first contact of the spermatozoon 
with the fertilization cone leads to the extrusion of a gelatinous 
mass which in the unfertilized egg lies under the perivitelline 
membrane. Lillie showed that by centrifuging the eggs at 
this stage the spermatozoon can be thrown off. In this case no 
further development of the egg follows. It should be pointed 
out that this contact action of the spermatozoon in Nereis is 
not comparable to the results of artificial membrane formation 
in the egg of the sea-urchin, since in the latter case the egg not 
only begins to segment but may reach the blastula stage if the 
temperature is low. 
6. Kupelwieser? succeeded in causing the development of 
the egg of sea-urchins by the sperm of molluses, Mytilus, 
Mactra, and Patella, and of annelids, Auduinia. In this case 
the spermatozoa entered the egg and often more than one 
spermatozoon entered, but no fusion of sperm and egg nucleus 
occurred. As a rule the first segmentation began only many 
hours (4 to 20) after the addition of sperm. The development 
was most abnormal and no plutei were obtained, as far as the 
writer is able to judge. Kupelwieser states that in these experi- 
ments no fertilization membrane is formed. If a fertilization 
membrane formed, the eggs did not develop. 
The writer found in 1908 that the eggs of the sea-urchin 
S. franciscanus could be fertilized by the sperm of a molluse, 
Chlorostoma, and that normal plutei of franciscanus were formed. 
His attempts in later years to obtain plutei failed. 
1 F. Lillie, ‘‘Studies of Fertilization in Nereis,’ Jour. Morphol., XXII, 361, 
1911. 
2 Kupelwieser, Biol. Centralbl., XXVI, 744, 1906; Archiv f. Entwicklungs- 
mechanik, XXVII, 434, 1909; Sitzungsber. d. Gesellsch. f. Morphol. u. Physiol. 
in Minchen, 1911. 
