300 EARLY DETERMINATION IN DEVELOPMENT 



urchin animalization and the enlargement of the amphibian noto- 

 chord (Ranzi, 1942). By arranging the various ions in the order 

 of their activity, it appears that they follow the lyotropic series of 

 Hofmeister. The greater the activity in inducing cyclopy (or vege- 

 talization) the greater the activity in precipitating the colloids. 

 On the other hand, ions with more swelling activity are more ac- 

 tive in inducing notochord enlargements (or animalization) 

 (Ranzi, 1943). This conclusion brings forth the supposition of a 

 direct action of substances that change embryonic determination 

 on protoplasmic ultrastructures. 



An attempt to examine this point directly was made by Abruz- 

 zese Sgarlata (1947). Unfertilized eggs of Arhacia were treated 

 either with NaSCN or with LiCl and then centrifuged. In NaSCN- 

 treated eggs stratification was faster than in controls; in LiCl- 

 treated eggs stratification was slower than in controls. This re- 

 search was confirmed and extended to fertilized eggs by Lallier 

 (1955). 



In order to study the differences between normal, vegetalized 

 and animalized frog embryos, we (Ranzi and Citterio, 1955a,b) 

 have studied the possibilities of extracting the proteins from 

 lyophilized embryos and of precipitating them by using the 

 "salting out" method of Derrien et at ( 1952 ) . With this method 

 we started to study the changes in proteins during normal em- 

 bryonic development. At first, during fertifization, and later, 

 dming the cleavage stages, the amount of protein extracted de- 

 creases. Furthermore, extracted proteins precipitate at a lower 

 concentration of ammonium sulfate. Myosin and actin antigen'- 

 appear during gastrulation. After this stage a gradual process of 

 protein differentiation occurs. New proteins with different char- 

 acteristics of precipitation appear. Plasma and red cell antigens 

 appear during neurulation. 



On the basis of these data the following experiment is possible. 

 Frog embryos are treated with LiCl or NaSCN at the sensitive 

 stage and then, after a thorough washing in fresh water, are freed 

 from jelly and are lyophilized. The fractions precipitating at dif- 

 ferent concentrations of ammonium sulfate are determined quan- 

 titatively (Fig. 10). In the young gastrulae, after a six-hour treat- 



