HISTORY OF ARTIFICIAL PARTHENOGENESIS 53 



a small amount (J to \ of 1 per cent) of KC1 is added to the 

 sea-water, the amphiaster of the first oocyte stage at once \ 

 resumes its activity. "The maturation processes, including 

 the extrusion of the first and second polar bodies and the 

 concomitant changes in the form of the egg, succeed one another 

 with the same regularity that obtains when the egg is fertilized." 

 Mead, however, observed no further development in these 

 eggs. From these experiments he concludes that, in the normal 

 fertilization of Chaetopterus, "the entering sperm stimulates 

 these mitotic activities in a similar manner, i.e., by exerting 

 a chemical influence on the egg and not by furnishing the egg 

 with the organs of division." This work of Mead's which, in 

 my opinion, occupies a distinguished position among cytological 

 treatises, has been but little noticed in the literature of the 

 subject. 



In 1899 Morgan 1 published some new and important obser- 

 vations on the effect of hypertonic solutions upon the unferti- 

 lized egg. He had discovered that if unfertilized eggs were 

 treated with hypertonic sea-water, they began to divide without, 

 however, developing into larvae. Morgan considered this 

 cleavage an abnormal phenomenon, which was in no w&y com- 

 parable to normal segmentation. "The form of the cleavage 

 is totally different from that of the normal cleavage." Accord- 

 ing to Morgan's illustrations, the eggs appear to have developed 

 to about the sixteen-cell stage, but not farther. "The time 

 that it takes for a cleavage plane to pass through the egg is 

 often very long in comparison to the time of normal division. 

 The result is a mass of extremely minute granules or pieces. 

 These pieces never acquire cilia and do not produce any form 

 that resembles any stage of the normal embryo. Later the 

 masses disintegrate" (pp. 454 and 455). Morgan's aim was not 

 to obtain artificial parthenogenesis, but to corroborate his former 



1 Morgan, "The Action of Salt Solutions on the Unfertilized and Fertilized 

 Eggs of Arbacia and of Other Animals," Archiv f. Entwicklungsmechanik, VIII, 448 

 1899. 



