146 S. J. HUNTER. 



of condensed sea-water for two hours and four minutes, resulting 

 in the appearance of many cytasters (Wilson) and the segmenta- 

 tion of many eggs, but no active larvae. Segmentation and de- 

 velopment ceased after four hours in the sterilized sea-water. 

 The ovaries of another female were teased in sea-water and a 

 small number of pale eggs were obtained. From the condition of 

 the ovaries, the color and the number of eggs it was evident that 

 the eggs were not mature (oocytes). These were placed for the 

 same length of time in concentrated sea- water and then transferred 

 to normal sea-water. More than 90 per cent, of these eggs reached 

 the active larval state. Eggs of females brought directly from 

 the bed of the ocean gave better results than those kept in the 

 laboratory aquarium for a time. The higher temperature of the 

 sea-water in the laboratory probably hastened maturation. It 

 became evident throughout the later series of experiments that 

 oocytes gave satisfactory results and ootids gave negative results. 

 It seems probable, therefore, that concentrated sea-water is effec- 

 tive in producing development in Arbacia only when its influence 

 is brought to bear upon the oocyte. 



The interesting question naturally arises concerning the exact 

 stasre at which the solution is effective. If this influence causes 



o 



retention of the second polar body and its assumption of the role 

 of the spermatozoon the subject is at once brought into direct 

 relation with Boveri's l theory of natural parthenogenesis. In 

 Delasre's 2 observations on the influence of carbon dioxide on 



o 



Astcrias he gives results to show that the moment of suscepti- 

 bility of the eggs lies between the time when the nuclear mem- 

 brane of the germinal vesicle begins to dissolve and the beginning 

 of the resting period of the egg nucleus ; and that the immedi- 

 ate cause does not concern the polar bodies but rather the 

 suspension of maturation for a given period. Upon resumption 

 the polar karyokinesis is not confined to one region of the egg, 

 but instead becomes general and includes the whole egg. Con- 

 sideration of this phase is curtailed by Delage's 3 own statement 



!Th. Boveri, " Zellstudien," L, 1887, p. 73. 



2 V. Delage, " Nouvelles Recherches sur la Parthenogenese Experimentale chez 

 Asterias glacialis," Archiv de Zool. Exper., 1902, p. 217. 



3 Y. Delage, "Etudes Experimentales sur la Maturation cytoplasmique chez les 

 Echinodermes," Archiv de Zool. Exper., 3 Ser., IX., 1901, p. 295. 



