126 THE PHYSIOLOGY OF EARTHWORMS 



rise after removal of the posterior fifth of the body, by 19% for 

 L. terrestris, 37% for E.foetida and 64% for A. longa in the first day. 

 This increase then gradually disappears and values return to 

 normal. The same operation on feeding animals leads to a small 

 transient decrease in total nitrogen excretion, but the absolute 

 values are greater. This represents a slight shock reaction which 

 quickly passes. Isolated posterior pieces show a nitrogen excretion 

 rate that increases over the 15 days following excision. 



The increase in nitrogen excretion is proportional to the amount 

 removed by operation and Fig. 37 shows that if the body is 

 bisected the anterior portion shows a rapid rise in total N output, 

 followed by a more gradual rise over 30 days. The posterior portion 

 increases its nitrogen excretion more rapidly followed by an 

 equally rapid fall and thenceforward shows a gradual decline till 

 death at 20 days. The ratio of ammonia and amine N to urea N is 

 high as in normal feeding worms [Lumhriciis). 



By removing diff'erent fractions of the same earthworm body 

 Needham finds that there is a gradient of N excretion along the 

 body with the greatest nitrogen output occurring towards the rear 

 end, in the penultimate one-fifth of the body. This corresponds 

 with several other physiological gradients reported previously in 

 Chapter IV. The posterior peak tends to be rather further forward 

 in fasting than in feeding worms. The details differ slightly from 

 species to species, but the broad outlines of the situation are similar 

 for L. terrestris, A. longa and E.foetida. 



Summary 



Regeneration is a common phenomenon in oligochaetes, though 

 in some cases lost segments are not replaced. The presence of the 

 ventral nerve cord is essential for regeneration to occur, its 

 removal preventing regeneration of the area affected. The electrical 

 axial field is disturbed by section but eventually recovers to the 

 initial situation. The acetylcholine production of the earthworm 

 body may be linked with regenerative ability. Mass migration of 

 the chloragogen can occur after bisection of the animal. The cells 

 break down in the area of the wound, releasing their contents. 

 Respiration of the tissues declines upon cutting but gradually 

 recovers. Metabolites, glycogen, lipids and pyruvic acid, for 

 example, are affected by section. Alkaline phosphatase appears to 



