

It is a fact generally recognized that in many cases of hybridi- 

 zation the dominance of Mendelian characters in the heterozygote is 

 incomplete. This incompleteness in development may be permanent 

 and give rise to intermediates; or it may be temporary, obtaining 

 only in the juvenile forms, later giving way to complete dominance 

 of the characters involved. 



With a view to getting rational insight into such cases the writer 

 has proposed a biochemical analysis of dominance *). The justific- 

 ation for such an assumption is that biologists as a rule accept the 

 fact of a biochemical basis for life phenomena. Thus LOEB 2 ) very 

 strikingly has shown that the action of the spermatozoon in fertilizing 

 an egg is chemical in character. ROBERTSON 3 ) has pointed out the 

 fact that the rate of growth of organisms may be interpreted as an 

 autocatalytic reaction. 



PnisiLAx 4 ) has proven that .the tyrosinase which he found present 

 in the larvae of the cockroach (Phyllodromia germanica) gives rise 

 to the pigment of the tegument by oxydizing tyrosin. In the newly 

 hatched larvae the tegument is white but during the following three 



1) MOORE, A. E., Univ. of Calif. Publ. Physiology. (1910.) Vol.4, p. 9 15. 



2 ) LOEB, J., Chemische Entwicklungserreg. des tierischen Eies. Berlin 1909. 



3) ROBERTSON, T.B., Arch. f.Entw.-Mech. Bd.25. S.581u.f. Bd.26. S.lOSu.f. 



4 ) PHISILAX, M. C., Comptes rendus soc. biol. (1905.) Vol. 59. p. 17. 



