20 UNIVERSITY OF MISSOURI STUDIES [2o8 



however, only negative. In several crayfish in which the bran- 

 chiostegite was cut away, the cut edge seemed to heal over, but 

 new setae did not develop. None of the individuals, however, 

 lived through a moult, and it can not be told with certainty 

 how much regeneration actually took place. In other crayfish 

 the carapace was removed from over the pericardial chamber, 

 but no indication of real regeneration was obtained, even when 

 the hypodermis was left uninjured and only the hardened shell 

 removed ; but here again I have never succeeded in keeping the 

 individual operated upon alive for more than two or three 

 weeks. In a number of crayfish a part of the exoskeleton was 

 removed from between the sterna and the abdomen. The wound 

 healed over in these cases and left an enlarged knob of tissue 

 covered by a brown cuticle. 



My experiments in removing the gills were never success- 

 ful. In order to observe the gills is was necessary to cut away 

 part of the carapace overhanging the gill chamber, and crayfish 

 operated upon in this way soon died. 



6. REGENERATION OF APPENDAGES FROM LEVELS OTHER THAN 

 THE SECOND JOINT. 



It very seldom happens that appendages are broken at any 

 joint except the one between the basipodite and the ischiopodite. 

 This is true not only of the chelipeds but also of the other ap- 

 pendages. Occasionally, however, a crayfish is found in which 

 a leg has been broken off at some other level. If this happens 

 in the chelipeds, the limb is usually thrown off later at the regular 

 breaking-joint, unless the injury occurs in the last one or two 

 segments. Then, no regeneration appears to take place and the 

 wound merely heals over, but at the next moult the appendage is 

 restored to a normal condition. I have only observed one in- 

 stance of the cheliped regenerating from any level other than the 

 breaking-joint. In this case the regeneration was taking place 

 from the distal end of the meros. 



