148 S. J. HUNTER. 



The eggs used in these experiments were not deposited natu- 

 rally, but were from ovaries removed from the female. 



The ovaries thus taken were of two kinds : first, dark red in 

 color, delicate in structure ; when placed in sterilized sea-water 

 eggs flowed freely from them without cutting or teasing ; second, 

 light red in color, firm in structure ; comparatively few eggs ob- 

 tained even after ovaries are cut and teased. 



The eggs from ovaries of the first class gave unsatisfactory re- 

 sults when subjected to influence of concentrated sea-water, satis- 

 factory results when fertilized with spermatozoa. 



The eggs from ovaries of the second category have given per- 

 centages as high as 80 to 90, of parthenogenetic swimming forms, 

 when subjected to influence of concentrated sea-water for the 

 proper period. 



Sections through ovaries, typical of this second class, reveal 

 large numbers of oocytes determined as such by the presence of 

 the prominent germinal vesicle. Sections through thirty-two 

 different follicles were examined. Only those showing germinal 

 vesicle (oocytes) or egg-nucleus (ootids) were counted. In these 

 thirty-two sections of follicles there were 183 oocytes and 85 

 ootids. 1 Oocytes much smaller than normal eggs were not 

 counted. The percentage of forms developed parthenogenetic- 

 ally is thus shown to bear a direct relation to the number of 

 oocytes in the culture. 



It seems reasonable, then, to infer that the concentrated sea- 

 water acts effectively upon the oocyte only. The exact nature 

 of this action it is hoped subsequent study will determine. 



Duration. The eggs of Arbacia, as is well known, are not suf- 

 ficiently transparent to permit close observation upon the activity 

 of the cell contents. For that reason I have been unable to note 

 in the egg any definite appearance which would signify the proper 

 moment for transference from condensed sea- water to sterilized sea- 

 water. In a few cases I have found wide variations in the time that 

 the eggs can be transferred and yet develop. The shortest time 

 was one hour and twenty-two minutes. The limits within which the 

 eggs from a given culture could be removed and yet develop were 



1 These follicles were from the ovaries of one female. Of the utilized eggs from 

 this female fully 75 per cent, became swimming larva;. 



