DEPARTMENT OF MARINE BIOLOGY. 1 35 



rapidly in body-size than others growing lesser amounts, and therefore the 

 new growing tissue must possess an excessive capacity for the absorption of 

 nutriment and may do so even at the expense and injury of the old body. 



EXPERIMENTS TO CONTROL REVERSAL OE ASYMMETRY IN THE REGENERATING 



CLAWS OF CRUSTACEA. 



Five species of the genus Synalpheus were used in the experiments. These 

 small Crustacea have the first pair of claws dissimilar in size and shape, one 

 claw being large and strongly developed, while its mate is small and weak. 

 Przibram and Wilson found that when the large first claw was removed at 

 the breaking-joint the small claw of the other side grew to be large and a 

 small claw regenerated from the stump of the previous large one; and thus 

 the asymmetry was reversed. The removal of both first claws was always 

 followed by regeneration of the large and small claws on their proper sides. 

 No evidence was found to show why this reversal took place or how it might 

 be prevented. 



I tested 50 individuals in order to satisfy myself that the 5 species selected 

 responded to removal of the first legs, as above stated. It was found without 

 exception that when only the big claw of the first pair was removed a small 

 claw always regenerated from its base, while the small claw of the other side 

 grew to be a large one. When both first claws were removed they invariably 

 regenerated in their original relations. 



P'irst, parts of the big chela were removed to determine how great a portion 

 of it was necessary to prevent reversal with regeneration. The large leg was 

 cut off at various levels, but after a day or so the entire leg was thrown off 

 from the breaking-joint when cut at any place more proximal than the base of 

 the most distal segment or the hinge of the pincer. Either part of the pincer 

 itself might be removed, or the entire pincer cut off, without subsequent 

 throwing off of the leg, and in all such cases the pincer was regenerated on 

 the big leg at the next molt, no reversal taking place. A method of slow anaes- 

 thesia might be employed by which other operations on the big leg could no 

 doubt be made without causing the leg to be cast off. 



Second, it was found in most cases that when both first legs were removed 

 at the breaking- joint and several other legs on the side of the big claw were 

 cut off, the big claw regenerated small and was equal in size to the regener- 

 ated little claw. This equality persisted after a second molt in several cases. 

 When either of these legs of equal size is removed the other grows into a 

 large leg and a small leg regenerates from the stump of the removed one. 



Third, when the large first leg is removed and several of the legs on the 

 side with the small first leg, then the small first leg does not always grow to be 

 large, but remains small and the first leg of the other side regenerates small ; 

 so here again both first legs are of equal size. In two cases several of the re- 

 moved legs on the little claw side failed to regenerate and in these cases it 

 is important to note that the first small leg grew to be a large one. 



Unfortunately the above results do not invariably follow, yet they seem to 

 suggest that a certain amount of reserve growth energy is necessary in order 

 that one of the first pair of legs may grow to form the large claw. Further, 

 this energy seems to be somewhat bilaterally distributed, so that when one 

 side is forced to regenerate several legs it is sometimes rendered incapable of 

 producing the first big claw. 



