284 BULLETIN OF THE BUREAU OF FISHERIES. 



blood, which coagulates and forms a protective crust over the stump. In a short time a 

 small white papilla, which represents the rudiment of the new limb, appears in the midst 

 of the brown, hardened clot. This papilla continues to grow independently of the 

 molting process, though covered with a cuticular membrane, until a miniature appendage 

 is formed. The papilla lengthens, and gradually the constrictions which mark the 

 future joints of the new limb make their appearance. At first colorless, the new 

 appendage becomes bright, transparent red, with bluish pigment at the constrictions of 

 the joints. In this stage the limb is surrounded by a thickening cuticle and soon ceases 

 to increase in size until after the next molt. If autotomy occurs just after a molt, the 

 appendage will reach a much greater size than if it happens a short time before, but 

 within the limiting period referred to below. 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. 



The large cheliped of the young lobster in the fifth stage may be regenerated in from 

 15 to 18 days after a single ecdysis, or it may require a month's time, during which the 

 animal may pass two molts. The normal size, however, according to Emmel, is not 

 attained until after the third molt. He also found that by the repeated removal of the 

 same appendage in sixth to eighth stage lobsters the rate of growth in the mutilated 

 limb was repeatedly reduced, but the experiment was not carried very far. This 

 observer has also found that the thoracic legs will not begin to regenerate if removed 

 immediately before a molt. The limit varies from 2 to 4 days in sixth to seventh stage 

 lobsters. In more mature animals the limiting period is 16 days at its shortest duration. 

 Accordingly, if accidents happen shortly before the molt, the animal must wait until this 

 crisis is over before nature can give any attention to the restoration of the parts lost. 

 Apparently in this case the energy required to renew the entire cuticular covering does 

 not leave any surplus immediately available for the growth of new limbs and tissues. 

 If the tips of the large chelipeds 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 propodus, it is usually cast off at the plane of fracture. 



The antennae are very liable to injury, particularly the delicate, sensitive flagella. 

 Autotomy does not occur in these appendages, but regeneration may take place at any 

 articulation in the flagellum or stalk. 



In the young the whip of the second antenna may be completely restored without 

 a molt taking place, while in the adult one molt at least appears to be necessary for com- 

 plete restoration. In the fifth stage lobster, already mentioned, the antennary flagellum 

 was restored in about 15 days. This appears first as a papilla or bud, which becomes 

 sickle-shaped and finally coiled so as to resemble a small spirally twisted red wax taper. 



The cuticle of the limbs in process of restoration must be elastic and capable of 

 considerable distension, although the limit of this distensibility is, in most cases, soon 

 reached. 



According to the studies of Miss Reed upon the process of regeneration in the crayfish 

 (^55) > the membrane or the inner half of the double fold which remains after autotomy, 

 and the blood cells beneath it serve to protect the end of the stump, but take no part in 



