IOS MAX M. ELLIS. 



form Mancasellus was chosen because it is abundant in this 

 region. It regenerates lost parts readily and as each leg has a 

 breaking joint at the coxal-thoracic articulation it is possible to 

 make all operations uniform. The results obtained are, in a 

 measure, parallel with Dr. Zeleny's work. 



II. Methods. 



The isopods used in these experiments were taken in a stream 

 near the Indiana University campus at Bloomington, from a part 

 not over three hundred feet in length. In this distance it is 

 probable that they had been subjected to the same general con- 

 ditions previous to the experiments. 



Set I. — For Set I. several hundred specimens were collected 

 on October 3, 1906, from which twenty normal males measuring 

 between 10-13 mm - were selected. These were divided into 

 four series. In series A a "standard" injury was established 

 by the removal of the right sixth walking leg. In each of the 

 remaining three series the operation was the infliction of the 

 "standard" injury plus an "added" injury. As "added" in- 

 jury the right fifth walking leg was removed in series B, the 

 right fifth, fourth and third in series C and all of the right thor- 

 acic appendages including the cheliped in series D. The opera- 

 tion was made in each series by pinching the tip of the appendage 

 to be removed till the animal cast it off at the breaking joint. The 

 above system was repeated daily on a fresh catch of Isopods for 

 five days, that is, until October 8, 1906, when the completed set 

 consisted of four series of twenty-five individuals each. Each 

 specimen was kept in a twelve-ounce saltmouth bottle, which 

 was inclined a few degrees from the horizontal by the mouth 

 resting on an inch block. The water was changed every six 

 days. As food, the partially decayed leaves of the common elm 

 were supplied. An excess of leaves was always present. Four- 

 teen days after the date of operation each individual was killed. 



Set. II. — The second set, series E, F and G, was planned 

 differently in order to obtain a uniform relation between the time 

 of the last moult and the date of operation. On January 24, 

 1907, several hundred isopods were collected and two hundred 

 and fifty normal males measuring between 13-16 mm. selected. 

 These were placed in individual bottles at once. Twenty-four 



