116 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



miles, maxillepeds, cheiipeds, walking-legs, the first pair of abdomi- 

 nal appendages (accessory reproductive organs), swimmerets, telson, 

 beak, and other parts of the carapace will be restored when injured. 



II. The power of regeneration at different levels in the thoracic 

 appendages. 



1 . The thoracic appendages have a varying power of regeneration 

 at different levels throughout the limbs. 



2. But this power is most highly developed at the "breaking 

 plane," i. e., at the joint between the second and third basal segments. 



3. The fact that this "breaking plane" is also the region at which 

 the limbs when injured are almost always autotomously severed 

 from the body leads to the conclusion that the comparative perfec- 

 tion of the power of regeneration at this region may be explained as 

 the result of natural selection. 



4. In these experiments it was found that the swimmerets re- 

 generated slower than the thoracic appendages; but it was also ob- 

 served that the swimmerets will regenerate sooner than the legs if the 

 latter were cut only a relatively short distance below the "breaking 

 plane." So it may be questioned whether the supply of food ma- 

 terial will explain the comparative difference in the restoration of the 

 thoracic appendages and the swimmerets. 



III. The attainment of normal length in the appendages. 



The antennae, maxillepeds, thoracic limbs, the first pair of abdomi- 

 nal appendages (accessory reproductive organs), and the swimmerets 

 did not attain the normal length at the first moult. 



The cheiipeds of very young lobsters were obser^'ed through the 

 first, second, and third moults with the result that the only case in 

 which the cheliped attained a normal size was at the third moult. 



IV. The effect of repeated removal of the same appendage. 



The right cheliped of sixth, seventh, and eighth stage lobsters were 

 repeatedly removed and regenerated. In the data obtained the given 



