INITIATION OF DEVELOPMENT IN CII.ETOPTERUS. 55 



chromosomes and nuclei, unaccompanied by cell-division, oc- 

 curred, followed by later cell-division with a regulation of the 

 nucleo-plasmic relation. 



There is very little in the literature relative to the physiological 

 cause of polar body formation in particular, aside from the 

 general question of parthenogenesis, but a few theories \\iih 

 regard to the retention or expulsion of the polar bodies and the 

 consequences to the egg, may be mentioned. Scott ('06) suggests 

 for Aniphitrite that potassium leads to the taking up of water by 

 the egg, that this tends to prevent the normal collapse of tin- <.-gg, 

 and thus also interferes with the formation of polar bodies. In 

 this connection he calls attention to the fact that in Chcetopterus 

 maturation is hindered by strong KC1, but not by weak potassium 

 chloride. 



Delage ('01) at one time thought that the retention of the 

 second polar body within the egg was an important factor in the 

 parthenogenesis of the star-fish egg, "en fournissant a 1'ceuf les 

 elements qui lui manquent," but later he changed this opinion 

 largely, his later view ('02) being that parthenogenetic develop- 

 ment depends on the arresting of maturation at some point 

 when the nucleus is in the mitotic phase. When the egg is re- 

 awakened, as it were, it proceeds to cleavage. In this way only 

 is artificial parthenogenesis dependent upon polar body forma- 

 tion. 



Loeb ('02) stated the necessity of free oxygen and OH-ions 

 in the sea-water in certain concentration to cause or accelerate 

 maturation in Asterias forbesii. He was able to prevent matura- 

 tion by a lack of oxygen or by adding acid or potassium cyanide 

 to the sea-water. The addition of sodium hydroxide or benzol 

 was found to induce maturation. Wolfsohn ('07) obsem-d 

 similarly for Acm&a that sodium hydroxide or fat solvents 

 brought about maturation, and that the passage of a stream of 

 hydrogen through the water inhibited it. Also "by stopping the 

 oxidative processes in the egg through the presence of potassium 

 cyanide, maturation can be inhibited." In these cases, then, it 

 would appear that maturation is bound up with oxidation 

 processes of some sort in the egg. 



In Chatopterns the matter is rather different. Not only is 



