336 



DEVELOPMENT OF ASCIDIANS 



treatment with a lithium salt. The larvae which developed after 

 such treatment had normal tails, but were without brains, sen- 

 sorial organs, and palps. 



In the ''Regulative" Eggs. The effects of the enzymatic block- 

 ing on organogenesis have been particularly studied in the sea 

 urchin egg. Many papers on this subject have been published by 

 Rulon (1949, 1950, 1951, 1952, 1955), who organized a well- 

 planned and systematic research. Rulon dedicated most of his 

 attention to the blocking of cytochrome oxidase, succinodehy- 



Fig. 12. Larvae of Physa. a, control; b to /, after treatment with 

 0.005% potassium cyanide (Mancuso, 1955c), 



drogenase, peroxidase, phosphorylases, and enzymes with sulf- 

 hydrylic radicals. He used, respectively, sodium azide, sodium 

 malonate, or maleic acid, sodium selenite, thiourea, glucose, and 

 zinc chloride. He obtained rather generalized abnormalities in 

 the larvae, which also can be produced with other treatments and 

 in that sense are not specific. For example, malonate does not 

 produce the abnormalities that are produced by sodium azide. 

 Both glucose and azide inhibit the phosphorylations, but their 

 effects on development are very different. The results obtained by 

 Rulon are certainly suggestive. However, one would like to know 

 something about the local distribution of these enzymes in the 



