124 THE PHYSIOLOGY OF EARTHWORMS 



wet wt. /hr and a considerable proportion of this oxygen uptake was 

 unaffected by potassium cyanide even in lethal concentrations. 

 The posterior two-fifths of the body was then removed and it was 

 found that the oxygen uptake rate remained virtually normal for the 

 first week of regeneration. Later, however, an increase of up to 

 85% was noted in respiration rates, and cyanide had little effect 

 upon any of this uptake. If regeneration was inhibited by irradiat- 

 ing the worms with X-rays no increase in oxygen uptake was ob- 

 served. In the first week of regeneration when no respiratory 

 increase is noted, mobilization and proliferation of neoblasts 

 occurs, and respiration does not increase even when new segments 

 increase in size since this happens after the late rise in respiration. 

 It is thought that the increase in respiration reflects morphogenetic 

 changes as it happens after initial mobilization of repair cells, but 

 before any increase in size. As the loss of weight shown by re- 

 generating worms is twice as great as that by intact worms kept 

 under similar conditions it is thought that the use of body stores 

 and metabolic cost is proportionately greater than that required to 

 maintain the animal in a status quo. 



The rate at which new segments are added during regeneration 

 is affected by cyanide, IQ-^M KCN initially raising the rate, IQ-^M 

 KCN depressing it. The eventual cessation of growth is not 

 affected and the remoulded body is the same with or without 

 KCN treatment. Worms kept in a low oxygen tension (less than 

 4% oxygen) in water regenerated slowly and in complete lack of 

 oxygen no differentiation occurred at all. High oxygen tensions 

 also blocked morphogenesis and were eventually lethal, but both 

 inhibition and lethal effect were alleviated by simultaneous treat- 

 ment with cyanide. This corresponds well with results obtained 

 by Fox and Taylor (1955) as reported elsewhere (p. 93). lodo- 

 acetate, an inhibitor of glycolysis, has no effect upon the rate of 

 oxygen consumption, but increases the rate at which the new- 

 segments develop setae, so called "later differentiation". It seems, 

 therefore, that each phase of regeneration has slightly different 

 processes involved, and that these differ somewhat from the normal 

 maintenance reactions of the body. In other words the demands 

 imposed by regeneration are added onto the already present basal 

 metabolism and require the use of specific enzyme systems to 

 provide the energy required for morphogenesis. 



