G. REVERBERI 337 



egg and on this point histochemical research is still largely want- 

 ing. 



Other research on the effects of the blocking of the a-keto- 

 glutarase or the aconitase by p-pyruvate or fluoroacetate in the 

 sea urchin egg has been recently published by Montgomery and 

 Bamberger ( 1955 ) . The inhibitors used do not produce any effect 

 on the first stages of development. The embryos arrest at the 

 blastula or early gastrula stages and do not differentiate — the 

 effects of the inhibitors seem to be of rather general character. 



In the regulative eggs extensive research has been conducted 

 on the amphibians. The eggs have been treated with many en- 

 zymatic inhibitors, for example, KCN, sodium azide, and anaero- 

 biosis, but as far as we know no localized, specific effects have 

 been observed. The blocking of cholinesterase, which is largely 

 present in the nervous system, was not followed by any abnor- 

 mality in that system (Boell, 1946). 



Conclusions 



It seems, from the above reported data, that one can affirm 

 with reasonable probability that some enzymes, at least, play a 

 role in morphogenesis. This conclusion emerges more clearly for 

 the mosaic eggs than for the regulative ones. In the latter, as 

 has been mentioned, the inactivation of the enzymes induces 

 abnoiTnalities of general rather than of specific character, as in 

 mosaic eggs. 



The question arises concerning the mechanism by which the 

 enzymes influence morphogenesis. I suppose that no one can 

 pretend at the present stage of the biological sciences to give a 

 plausible answer to that question. However, on the basis of the 

 data presented above, we would like to offer the following inter- 

 pretation. As we know, every morphogenetic character is under 

 the control of the genes. Where then does the morphogenetic 

 effect of the mitochondrial enzymes enter the picture? As Brachet 

 (1952, 1954) pointed out in several of his papers, the nucleus is 

 the site where nucleotides, either "nucleic acids or coenzymes" 

 (Brachet, 1954, p. 96) are synthesized. It is quite possible that 

 some of these coenzymes activate some mitochondrial enzymes. 



