G. REVERBERI 335 



that the embryos of this mollusc possess in the mantle and in the 

 shell gland a KCN-sensitive oxidase, probably a M-Nadi oxidase. 

 The treatment of the eggs with KCN, which blocks the enzyme, 

 gives rise to embryos with defective or rudimentary mantles and 

 shells (Fig. 12) (Mancuso, 1955c). 



However, we can add more evidence to the above results in 

 the ascidian egg. This evidence comes from experiments on the 



d e f 



Fig. 11. Larvae of Phijsa (schematic representation of the heads). 

 a, control; b to /, after treatment with 0.5% sodium azide for 4 hours (Man- 

 cuso, 1955b). 



development in anaerobiosis (De Vincentiis, unpublished). In a 

 partially oxygen-deprived atmosphere, that is, in conditions in 

 which the cytochrome oxidase is poorly active, larvae develop 

 which again are abnormal for the tail but normal for the "head," 

 as in the case of the azide-treated larvae. 



Finally, to remove any objection to the specificity of this 

 result and of the ones reported above, we shall mention some data 

 obtained by Farinella-Ferruzza ( 1955 ) in ascidian eggs after 



