Analysis of the relations between metabolism and morphogenesis requires that each set of processes be separated into component parts. Metabolism may be fractionated by means of agents of which the effects on particular enzyme systems are reasonably well known and the relation of the activity of such systems to morphogenesis may then be tested. In the annelid, Tubifc.r tubijcx, morphogenesis during posterior regeneration may be measured fractionally and "rate of localization," "rate of early differentiation," and "rate of later differentiation" expressed quantitatively (Collier, 1947). It was found that oxygen consumption and loss of weight by SUMMARY 1. Continuous exposure of regenerating Tubifc.r tubife.r, Mull, to cyanide has been found to affect "rate of localization" without affecting the ultimate extent or perfection of localization or of other morphogenetic processes.2. Continuous exposure to iodoacetate has been found to increase "rate of later differentiation" without having other effects on regeneration.