Vol. XXXV. November, !Ql8. No. 5. 



BIOLOGICAL BULLETIN 



EXPERIMENTS ON THE DETERMINATION OF THE 



FATE OF THE GRAY CRESCENT MATERIAL 



IN THE FROG EGG. 







W. C. GEORGE, 



DEPARTMENT OF BIOLOGY, PRINCETON UNIVERSITY 







In the latter part of March of this year I began a series of 

 experiments at Princeton University, having for my aim the 

 determination of the location of the organ-forming substances, 

 if such exist, in the cytoplasm of the frog egg. The work is 

 scarcely more than begun and I should not ordinarily venture to 

 present my results in such an incomplete form, but since I am 

 leaving Princeton to enter army work it seems advisable to give 

 a preliminary account of such results as I have obtained thus far. 

 I hope to be able to do further experiments at a later time and to 

 publish a full account with figures. 



The method used in these experiments was to inject small 

 amounts of a three-fourths of one per cent, aqueous solution of 

 trypan blue, a colloidal vital (?) stain, into the cells of the 

 early cleavage stages of the egg and into certain regions of the 

 young blastula. Injections were made under a binocular dis- 







secting microscope by means of exceedingly fine pointed glass 

 pipettes in which the large upper end was sealed. By warming 

 the upper end of the pipette part of the air would be driven out 

 and during cooling a quantity of the stain could be sucked in. 

 On rewarming, the stain would be forced out in a steady flow and 

 by inserting the needle into the cell or region that I desired to 

 inject a small amount of the stain would be left in the egg. 



Since no sections have been made as yet I cannot give any 

 report in regard to the distribution of the stain to the daughter 

 cells in those cases where the presence of the stain or the mechan- 



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