38 THE PHYSIOLOGY OF EARTHWORMS 



parameters also apparently showed a graded rise and fall over 

 body length. The extractable sulphydryl and sulphur content and 

 iodine equivalence values all showed a peak concentration at about 

 the point where a divided worm grows either forward or backward 

 depending upon the aspect of the cut surface. The concentrations 

 fall on either side of this point and the curve does not resemble 

 that of oxygen uptake. Unfortunately Perkins's graph has no 

 numerical information and there is no indication as to the methods 

 used. 



Criticism of these results and others similarly inclined upon 

 such groups as the planarians, led Shearer (1930) to re-investigate 

 the respiratory uptake using a manometric technique, more 

 delicate than his previous method. As a result of this work he 

 withdrew^ his previous conclusions completely and suggested that 

 the apparent differences between anterior and posterior pieces are 

 due to diiferences in motility, i.e. the slices from the anterior end 

 tend to move around the reaction vessels more rapidly than the 

 posterior pieces, the anterior fragments therefore metabolize 

 quicker and consequently the oxygen uptake is faster. He noted by 

 eye that the muscular activity of anterior slices was more pro- 

 nounced, but he used rather larger fragments than is advisable in 

 Warburg methods. 



Much smaller pieces were used by Maloeuf (1936b). He isolated 

 fragments (20-30 mg) into Frog Ringer and used the Warburg 

 method to obtain the respiratory rate at 30 °C, a temperature 

 higher than anything liable to be encountered by Liimhricus in 

 the course of its daily life in temperate regions, and shown later to 

 be above the thermal death point for L. terrestris, (28 °C) (Hogben 

 and Kirk, 1944; Wolf, 1940). His results showed that there were no 

 consistent differences in respiration of slices taken from different 

 regions, except that the anterior end respired more slowly than the 

 posterior end. The size of the pieces used was small enough to 

 eliminate co-ordinated movement and thus all the respiratory 

 rates were reduced to similar values, a fact also conspired by the 

 high temperature which would tend to destroy the metabolic 

 activity of the pieces. Watanabe (1927) described U-shaped 

 gradients for carbon dioxide production, oxidizable substances, 

 electrical potentials and total soUd content along the longitudinal 

 axis of the body wall of Pheretima hilgendorfi and Eisenia foetida, 



