REGENERATION OF LOST OKUANS. 



123 



(Fig. 85, ar.) It afterwards increases from one end to the other more 

 equally in length than in width, and nineteen or twenty days afterward, 

 with a tarentula of middle age, it presents an organ long, almost com- 

 pletely formed, gradually diminishing from the base towards the extremity, 

 and much twisted. The articulations of this organ are formed successively 

 from the base towards the periphcra, the second forms after the first, the 

 third after the second, etc. Consequently, this process is accomplished 

 nearly as that described by Clarapede 1 for Lycosids in their embryonic 

 period. Thus is accomplished successively the isolation of the tissues be- 

 tween the base of the joint and its extremity. Pending this, near the base 

 of the foot, one readily observes muscular fibres (Fig. 83, pt 1, and Ms.n), and 

 on the surface a chitinous membrane (ct.n), a little elongated at the base. 

 (Fig. 83, pt 2.) Here one does not notice that the muscles are isolated, or 

 anything but chitinous teg- 

 ument (ct.n) ; the tip of the 

 foot (pt 3) only the chitino- 

 genous layer is isolated. 



Sections of this new 

 organ at different stages of 

 its development show that 

 it first originates the ma- 

 trix of the papilla ; its cells 

 at its periphera are in im- 

 mediate contact with the 

 blood, environing the neo- 

 formation. In the mean- 



Flii. 84. 



FIG. 85. 



SERIES SHOWING THE GRADUAL DEVELOPMENT OF THE NEW LIMB 

 WITHIN THE OLD STUMP. 



time, as the neo- 



Fit;. 84. Side view, showing on the retracted matrix, Mt, a small 

 papilla, pt, the beginning of the new leg. Flo. 85. A further 

 stage of growth ; ar, base of the new organ. Fi<;. 86. New limb 

 just before the moult, folded up within the stump. Other let- 

 ters as above. (After Wagner.) 



lime, as me iieo- 



formation grows, the exterior layer of the matrix is more and 

 Hairs more feebly colored ; at this epoch the superficial part may be 



regarded as chitinous tegument. The tegument is very fine, and 

 does not form simultaneously upon all the neoformation, but gradually, its 

 growth extending from the base towards the periphera. Thus the neofor- 

 mation presents, from the exterior inwardly, first, a chitinous tegument ; 

 second, a chitinogenous layer beneath it; third, the matrix. Within the 

 latter the hairs originate from elongated trichogenous cells, in no way 

 differing from that already described during moulting,' 2 except, of course, 

 that no sheath of the old skin appears in the process. 



The above statements present the general features of the processes from 

 which results the regeneration in spiders of a lost organ. Mr. Wagner adds 

 the following deductions: 1. The blood corpuscles, under the influence 

 of certain conditions, are subject to metamorphosis, the final result of 

 which is the formation of a tissue which resembles chitine. 2. The 



Recherches sur 1'evolution des Ataignees. 



2 See Chapter V., Fig. 13. 



