230 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 



5. F. Lillie 1 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 2 succeeded in causing the development of 

 the egg of sea-urchins by the sperm of molluscs, 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 mollusc, 

 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 Miinchen, 1911. 



