10 LIBBIE H. HYMAN AND ALBERT E. GALIGHER 



ences concern the relative, proportions and sizes of the parts of 

 the animal at different levels. Even such differences are practi- 

 cally nil between the first two pieces, as the diameter of body and 

 digestive tract and length of segments are much the same through- 

 out the anterior half of the worm. 



By reference to the graphs in figure 1, it will be seen that pieces 

 1 and 2 are cut from the descending part of the gradient and that 

 piece 3 generally includes the zone of autotomy when present. 

 The lowest part of the gradient of Lumbriculus falls between the 

 thirtieth and sixtieth segments. In order to avoid with certainty 

 the ascending gradient of the posterior two-thirds of the body, 

 the second pieces were cut well in the anterior part of this region 

 of lowest rate. It is of course impossible to know the details of 

 the gradient in each individual worm, and hence considerable 

 variation in the total oxygen consumption per unit weight in 

 different sets of pieces may be expected. It is nevertheless 

 certain that the oxygen consumption will be correlated with the 

 levels from which the pieces are taken. 



As Lumbriculus is rather small it was necessary to cut a con- 

 siderable number of pieces for each experiment. A count of 

 the number of pieces was not made, but the number was prob- 

 ably in the neighborhood of two hundred. All of the pieces 

 from each level were placed in a 500 cc. Erlenmeyer flask. This 

 was filled air tight with water, of which a sample was taken for 

 analysis. The flasks containing the pieces were then allowed 

 to stand at constant temperature for twenty-four hours. In 

 some experiments the pieces were- cut in the morning and the 

 experiment run from the afternoon of one day to the same time 

 of the following day. In other cases the pieces were prepared 

 late in the afternoon and the experiment begun the next morning. 

 The second procedure was planned to eliminate any stimulation 

 due to section if such might be present, but gave the same general 

 results as the first plan. After the twenty-four-hour interval 

 a sample of water was drawn from each of the experimental flasks 

 and its oxygen content determined. The oxygen content was 

 analyzed by Winkler's method. Further details will be found 

 in previous publications (Hyman, '19). The pieces of worms 



