1 54 REGENERA TION 



Regeneration may take place from any region, but, as yet, no obser- 

 vations have been made on the relative rate of growth of the new 

 arm at different levels. 



One of the most remarkable cases of autotomy is that in holothu- 

 rians, in which the Cuvierian organs, and even the entire viscera, may 

 be ejected when the animal is disturbed. A new digestive tract is 

 regenerated. 1 



It is known that several of the myriapods lose their legs at a defi- 

 nite region near the base, and that they have the power of throwing 

 off the leg in this region if it is injured. I have often observed that 

 the legs of Scutigera forceps are thrown off if they are held or injured, 

 and even when the animal is thrown into a killing fluid. Amongst the 

 insects the plasmids or walking-sticks also throw off their legs at a 

 definite joint, as described by Scudder, and more recently by Bor- 

 dage, and still later by Godelmann. New legs are regenerated 

 from the stump of the old leg, as has long been known. 2 Other 

 insects do not have the power of throwing off their legs, and we have 

 only a few observations that show that the legs if lost can be regen- 

 erated. It is known in the cockroach that the tarsus can regenerate 

 if lost or if cut off, and that fewer segments are regenerated than are 

 present in the normal animal. Newport found that the true legs of a 

 caterpillar are regenerated during the pupa stage if they have been 

 previously cut off. 



A further example of autotomy is found in the white ants, which 

 break off their wings at the base after the nuptial flight. There 

 exists a definite and pre-formed breaking-plane in this region. 

 The true ants also lose their wings after the nuptial flight, but there 

 does not seem to be a definite plane of breaking, so that the process 

 can scarcely be called one of autotomy. These cases also differ from 

 the other cases of autotomy in that the lost parts are not renewed. 



It has been observed 3 that if the leg of tarantula is cut off at any 

 other place than at the coxa, the animal bites off the wounded leg with 

 its jaws down to the coxa. In other spiders this does not occur, 

 although Schultz has observed that when the legs are lost under nat- 

 ural conditions they are found broken off in most cases at the coxa. 

 Schultz has also found that the legs regenerate better from this 

 region than from any other. It would be rash, I think, to conclude 

 without further evidence that the habit of tarantula to bite off a 

 wounded leg down to the coxa has been acquired in connection with 

 the better regeneration of the leg at this place. It is possible that 

 the injury may excite the animal to bite off the leg as far as possible, 

 which might be to the coxal joint. It would certainly be very remark- 



1 The phenomenon has been observed by Dalyell, Semper, Minchin, and others. 

 8 Miiller, Elements of Physiology, 1837. 8 By Wagner ('87). 



