294 MORGAN. [VOL. I. 



were forming, and three others had the beginning of a bud. In 

 three cases in which the tip of the leg had been cut off no new 

 part formed. As these legs were in constant use, any new 

 tissue would, perhaps, even if it formed, be worn off. 



From another series one of the last two thoracic legs or the 

 first, second, or third abdominal appendage was cut off on June 

 12. On July 2 the crabs were killed and examined. Thirty-one 

 individuals were present at the end of the experiment, and of 

 these five were regenerating the fourth leg, and four showed as 

 yet no signs of regenerating the lost leg; six were regenerating 

 the fifth leg; three were regenerating the first abdominal append- 

 age, but nine showed no signs of regeneration in this appendage; 

 two were regenerating the second abdominal appendage (<?), 

 and four were not regenerated ($). 



Summary. - -The results show that the small fourth and fifth 

 legs possess the power of regeneration. The abdominal append- 

 ages (first, second, and third) have also the power of regenera- 

 tion, but the percentage of those in which the process takes 

 place is smaller than in the case of the thoracic appendages. 

 Whether this difference is due to the longer time necessary for 

 these appendages to grow again or to some difference connected 

 with the place at which they were cut off is not clear. Whether 

 a molt is necessary for the reappearance of the abdominal 

 appendages I do not know. It may be that they do more rarely 

 regenerate, and this in turn may be connected in some way with 

 the amount of food supply brought to the region from which 

 they arise. At any rate, the positive result in those cases 

 where regeneration took place shows that these appendages 

 still possess the power of regeneration. 



In another experiment one of the last abdominal appendages, 

 the right or the left, was cut off on June 14. On July 2 all, 

 with one exception, were regenerating. Eight individuals had 

 a new, or regenerating, left appendage, and the right smaller 

 appendage was regenerating in three cases. In a single case 

 the absent right appendage had not regenerated. 



In the second series of experiments, made on August 18 and 

 brought to a close on September 15, the eyes, antennae, 



