334 



DEVELOPMENT OF ASCIDIANS 



Fig. 9. Hatched Ttibifex worms, a, control; h, c, after treatment with 

 1 X 10-2 ]Vf sodium azide (Palazzo, 1955). 



is, the mesodermic cell. Palazzo ( 1955 ) partially blocked the 

 CO. with sodium azide in the first stages of development. She 

 obtained worms with relevant deficiencies in the muscular system 

 and in the circulatory system, both of which are mesodermic 

 derivates (Fig. 9). 



In the eggs of Bithynia (Attardo, 1955a) and Physa (Mancuso, 

 1955a), however, the CO. appears localized in the ectodermic 

 blastomeres. Now the blocking of the enzyme by sodium azide 

 (Figs. 10 and 11) produces animals which are abnormal for the 

 ectodermic derivates, i.e., the brain, the eyes, and the tentacles 

 (Attardo, 1955b; Mancuso, 1955b). 



Another example of relations between the enzymes and mor- 

 phogenesis is offered by the Physa egg. Mancuso ( 1955a ) showed 



Fig. 10. Larvae of Bithynia. a, control; b, c, after treatment with 7 X 

 10~2 ]Vf sodium azide for 4 hours, at the earliest stages of development 

 (Attardo, 1955b). 



