Artificial Parthenogenesis i7i Thalassema Melltta 93 



My purpose in undertaking this research has not been primarily 

 to analyze the physiological processes involved, but rather to study 

 the morphological phenomena concerned in artificial partheno- 

 genesis, and especially, by a careful cytological examination of 

 the material, to compare, as far as possible, the development arti- 

 ficially produced with the normal events leading up to the forma- 

 tion of the larva. My attention, therefore, has not been mainly 

 directed to an investigation of the nature of the action which 



O 



parthenogenetic agents exert upon the egg, nor to an exhaustive 

 study of the conditions under which such agents act, although in 

 the course of the experimental part of the work a number of in- 

 teresting facts have bedn brought out and noted. After having 

 discovered that acids in dilute solutions could cause the formation 

 of swimming larvae, I did not attempt to extend the method, as it 

 seemed adequate for my purpose. 



II ARTIFICIAL PARTHENOGENESIS IN ANNELIDS 



Artificial parthenogenesis has been observed in the case of 

 several other annelids by a number of experimenters. Loeb ('01) 

 first succeeded in causing development of the unfertilized eggs of 

 Chaetopterus by increasing the osmotic pressure of the sea-water, 

 by the action of KCl and other potassium salts in the absence of 

 the osmotic effect, and by exposure to dilute solutions of HCl. 

 By all of these means he obtained swimming larvae which he 

 states presented an appearance exactly like that of normal trocho- 

 phores arising from fertilized eggs. Inasmuch as the changes 

 leading up to the formation of these swimming structures were 

 totally different from normal, developmental phenomena, and as 

 the trochophore stage was apparently reached without visible signs 

 of cleavage, Loeb concluded that normal cell lineage is an entirely 

 secondary phenomenon. The structure of these swimming larvae 

 of Chaetopterus was afterwards carefully examined by Lillie, whose 

 observations will be referred to below. In the same paper, Loeb 

 states that he also produced certain changes in the unfertilized 

 eggs of Phascolosoma and Podarke, the former dividing into 30 to 

 60 cells, while in the latter only the first cleavage occurred. 



