THE AMERICAN LOBSTER. 105 



bluish pigment at the constrictions of the joints (fig. 182). In this stage the limb is 

 surrounded by a thickening cuticle and soon ceases to increase until after the next 

 molt. It may, according to Brook, attain a length in young lobsters of 1^ to li inches. 

 If autotomy occurs just after a molt, the appendage will reach a much greater size 

 than if it happens a short time before. When the molt finally takes place the new 

 stump becomes very much larger and now resembles the normal appendage in all 

 respects except size. With each succeeding molt the normal size is gradually 

 attained. 



Two stages in the regeneration of the large cheliped of the larva already referred 

 to (No. 23, table 34) are illustrated in figs. 92, !t(i. After a period of 15 days, during 

 which time two molts had occurred, this limb had become completely regenerated. It 

 was reproduced in 12 days after the emergence of the papdlary bud. 



A larva in the fifth stage, length 15 mm., was placed under observation July 28, 

 when the first right cheliped was clipped off. On August 12, 15 days after the injury, 

 the animal molted and the cheliped appeared restored. The lobster was now 17 mm. 

 long. The length of the sixth joint— propodus — of this rudiment at the time of the 

 molt was 2 mm., while the length of the same joint of the limb after ecdysis was 

 4.V mm., and the length of the corresponding joint of the unimpaired limb was 5 mm. 

 In this case the new limb had been developed during a single molting period to nearly 

 its normal size. 



A similar result was obtained in the following experiment: A fifth larva, length 

 15 millimeters, was placed nude]' observation on July 28, and the first right cheliped 

 was clipped. The right antennary flagellum had been previously cropped close to the 

 stalk, from which a new bud was growing; 6 days later, on August 3, the sprouting 

 antennary flagellum was coiled, and a very small bud represented the right cheliped. 

 August 12, 15 days after the first observation, the fiagellum of the second antenna on 

 the right side was nearly normal in appearance and size. The rudiment of the right 

 cheliped was segmented, and about 3 mm. long. This larva molted on or near August 

 15, or 18 days after mutilation, to the sixth stage, when it attained the length of 18 mm. 

 The right cheliped was regenerated, but, as in the other case, it was somewhat smaller 

 than the other. The measurements are as follows: 



Regenerated right first cheliped: Length of propodus, 5 mm. ; greatest width, 1.3 mm. 

 ITnimpairefl left first cheliped: Length of propodus, 6 mm. ; greatest width, 1.5 mm. 



On the one hand, the large cheliped of the young lobster may be regenerated in 

 from 15 to 18 days, and after a single ecdysis, and on the other it may require a 

 month's time, during which the animal has molted twice. 



The time required for the renewal of a limb thus depends npon the time at which 

 an injury occurs with reference to the molt, and also npon the physiological condition 

 of the animal. If the tips of the large chelqieds are clipped off, autotomy does not 

 always or usually occur, and the limb is completely repaired after one molt. If the 

 limb is injured below the sixth joint (propodus or large joint of claw in cheliped), it is 

 usually cast off at the plane of fracture. 



REGENERATION OF ANTENNA AND OTHER APPENDAGES. 



The antenme are very liable to injury, particularly the delicate, sensitive fiagella. 

 Autotomy does not occur in these appendages, so far as is known, but regeneration 

 may take place at any articulation in the flagellum or stalk. 



