W. W. SWINGLE 595 



The fact that the iodine was in alcoholic and the bromine in aqueous 

 solution had no effect on the results obtained. This is clearly shown 

 elsewhere where similar results were obtained and an alcoholic solu- 

 tion was not used.' Five cultures of larvae received gradually in- 

 creasing amounts of iodine and bromine. Thus Bromine Culture 1 

 received 2V cc. of m/10 stock solution of bromine in 2,000 cc. of 

 H2O, yielding m/460,000 solution. Iodine Culture 1 received ^ cc. 

 of stock solution iodine in 2,000 cc. of H2O, making m/1, 100,000 solu- 

 tion. More drops of the alcoholic solution are required to make 1 cc. 

 than of the aqueous solution due to the difference in surface tension of 

 the two solutions, hence the difference in the size of the drops. Cul- 

 tures 2, 3, 4, and 5 of the bromine set received respectively -i^, -rz, 

 -2%, and T3 cc. of the m/10 solution. Cultures 2, 3, 4, and 5 of the 

 iodine set received respectively ^5, ye^ TK ^^^ 5^ of the m/10 solution 

 iodine. Bromine Culture 2 compares, in regard to strength of 

 solution used, with Iodine Culture 4, though the iodine culture is con- 

 siderably the weaker. An exact chemical equivalent solution falls 

 somewhere between Bromine Cultures 1 and 2 and Iodine Culture 4. 



It is probably not necessary that iodine or bromine obtain en- 

 trance to the organism through the alimentary tract; they will prob- 

 ably be absorbed and reach the vascular system almost as rapidly 

 through the integument.^ 



Observations. 



Experiment 1. Iodine Feeding. — The tadpoles, fasting since their 

 emergence from the egg jelly, measured 10 mm. in length, and showed 

 no indications of limb buds when first fed iodine. There were six 

 cultures, one serving as control for the other five. There was no 

 change during the first 32 hours in Cultures 1, 2, and 3, some mor- 

 tality in Cultures 4 and 5, especially in 5. At the end of 60 hours 

 the larvae in Cultures 4 and 5 showed, on microscopic examination, 

 considerable fraying of the delicate tail-fin and extravasation of blood 



^ McClure, C. F. W., On the behavior of Bufo and Rana toward colloidal dyes 

 of the acid azo group, American Anatomical Memoirs, No. 8, 1918. Swingle, 

 W. W., On the experimental production of edema by nephrectomy, /. Gen. 

 Physiol, 1918-19, i, 509. 



