S. RANZI 305 



that Leone ( 1952, 1953 ) found an enlargement of the notochord 

 m amphibians to be induced by urea, a well-known denaturing 

 agent. The formation of notochord and neural rudiments in ex- 

 planted ventral pieces of young gastrulae can be induced by 

 urea. 



Action of Vegetalizing Agents 



Vegetalizing substances do not change considerably the afore- 

 mentioned properties of proteins; the flow birefringence is not 

 altered; the intensity of OH and phenolic group reaction is not 

 increased (Arosio and Bossi, 1954). 



The action of vegetalizing substances becomes evident from 

 another type of experiment. We take into consideration the action 

 of a strong denaturing agent such as urea on proteins treated with 

 animalizing or vegetalizing substances. Two samples are pre- 

 pared of a solution of euglobulin a + b from sea urchin eggs 

 (Fig. 14). A certain quantity of an animalizing or vegetalizing 

 substance sufficient to induce an alteration in the embryonic de- 

 velopment is added to one sample. For example, by using LiCl 

 as a vegetalizing agent, 86 parts of IM KCl plus 14 of IM LiCl 

 are added to 100 parts of the first sample ( tube 2 ) . To the other 

 sample the same amount of IM KCl is added (tube 1). After 

 overnight storage in a cold room we assume that the sample 

 treated with LiCl is vegetalized. The proteins of the second sam- 

 ple are assumed to be proteins of the normal embryo. From both 

 samples we prepare two samples of 5 ml each. Then 0.6 ml of 

 IM KCl are added to one sample (tubes 3,5) and 0.6 ml of 30% 

 irrea is added to the other sample (tubes 4,6). The viscosity read- 

 ings are taken after four hours immersion in the viscosimeter 

 bath. The treatment with vegetalizing substances, as mentioned 

 before, induces an increase in viscosity. Now it is possible to 

 show another fact. The viscosity decreases in the sample with 

 urea and the rate of decrease in proteins treated with vegetaliz- 

 ing agents is lower than in the controls. On the other hand, the 

 rate of decrease in viscosity of proteins treated with animalizing 

 agents is much higher than in the controls (Ranzi and Citterio, 

 1954). These data (in Fig. 14) show the greater resistance of 



