952 ME. H. U. BlllNDLEX ON REPRODUCED [Dec. 13, 



of reproduction executes the proper work however much or how- 

 ever httle may he the amount of material placed at' its disposal. 

 The suggested factor of insufficient nutritive supply is moreover 

 no explanation of why in some genera or groups of genera the 

 new growth is constantly a true " reproduction " in that it exactly 

 resembles the normal, while in other genera or groups of genera it 

 as constantly assumes a form which is strikingly different from 

 the normal. And granted that parts subject to loss have their 

 reproduction ensured by a special adaptation of the nutritive and 

 trophic supphes appropriated to them, there is no solution yet 

 possible of why reproductions which are unlike the normal should 

 exhibit a degree of fixity and trueuess to type which in the case of 

 normal congenital structures we are accustomed to regard as the 

 outcome of selection. 



In summary of what has been said it seems to be the case 

 that : — 



(i.) In Arthropoda generally the power of reproducing a lost or 

 injured appendage is partial in so far that the basal portion of the 

 appendage must be left to inaugurate the new growth, reproduction 

 of the entire appendage by the trunk being not possible. 



(ii.) The power of reproduction seems to be possessed con- 

 currently with the ecdyses and to be relinquished when these no 

 longer occur. 



(iii.) In Crustacea the reproduced portion of an appendage can 

 be observed growing out from the stump, being covered with a 

 thin cuticle specially formed over it. In Tracheata the reproduced 

 portion does not become revealed till ecdysis, being entirely hidden 

 hv the cuticle of the region proximal to the place of amputation. 

 There is some evidence that in many cases the elaboration of the 

 reproduced portion is a rapid process taking place only just before 

 ecdysis. 



(iv.) Subject to certain objections to regarding the reproduced 

 appendage of a Tracheate Arthropod as invariably of the nature 

 of a bud from the stump, in some forms reproduction may 

 commence from almost any part of any joint, while in others 

 autotomy or else the dropping away of portions of the stump 

 subsequently to injury determines that reproduction shall commence 

 only from very few regions or even only from a single region. 



(v.) In Crustacea the repi'oduced portion of an appendage is, 

 with reservations as to certain doubtful and exceptional cases, an 

 exact counterpart of the congenital structures it replaces. This 

 is also constantly the case with certain appendages in certain 

 Tracheata. 



(vi.) In certain appendages of some Tracheata the reproduced 

 portion is constantly unlike the normal, being distinguished there- 

 from mainly as follows : — 



(a) The number of joints is less than those which have been 

 lost, and is one less in cases where the normal number is 

 not more than six. 



