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 1J 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 clieliped of the larva already referred 
to (No. 23, table 34) are illustrated in figs. 92, 96. 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 papillary bud. 
A larva in the fifth stage, length 15 mm., was placed under observation July 28, 
when the first right clieliped was clipped off. On August 12, 15 days after the injury, 
the animal molted and the clieliped 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 
44 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 under 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 light cheliped. 
August 12, 15 days after the first observation, the flagellum 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. 
Unimpaired 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 upon the time at which 
an injury occurs with reference to the molt, and also upon the physiological condition 
of the animal. If the tips of the large cheliped s 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 ANTENNAE AND OTHER APPENDAGES. 
The anteume are very liable to injury, particularly the delicate, sensitive flagella. 
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. 
