44 



I gather that in 1900 (Prof.?) Gustav Tornier advanced a hypo- 

 thesis as to supernumerary parts of legs and antennje in beetles (I 

 have only seen the resume of his paper in the " Zoologischs Central- 

 blatt"). So far as I grasp his view, it is that these additional parts 

 are the result of a wound. He supposes that when the appendage 

 is wounded the regeneration centre that is reached may produce, as 

 an outgrowth from the wound as it heals, the additional joints : 

 two wounds may produce two new sets, and so on. To this 

 hypothesis I am quite willing to agree as possibly giving the explana- 

 tion of some instances, but he does not say anything of the complete 

 removal of the limb (or a portion of it) and the regeneration of a new 

 limb, with, upon occasions, superfluous joints ; he seems to regard 

 the double (or treble) appendages as being the original limb with an 

 outgrowth. The more usual cause, in my opinion, is somewhat 

 different. A portion of a limb is, say, bitten off by some enemy, and 

 it is regenerated ; most usually tlie limb is replaced, so that no result 

 of the injury is apparent. When, however, the injury takes place at a 

 late date in the life-history, and there is no time for the segmented 

 limb to reach its full size, a limb of reduced dimensions results. 

 Sometimes it is deformed, and more rarely it is duplicated or tripli- 

 cated ; these results are due to the germinal material reserved for 

 regeneration being damaged or divided at the time of the injury. 



In the Lepidoptera, if a leg or antenna be amputated — and 

 the wings come largely under the same rule—the part is grown 

 afresh. This does not occur all at once, and the progress made in 

 the interval is revealed at each following moult ; a leg amputated in 

 a very young larva is renewed so that the imago shows no difference 

 from a normal specimen, but if the injury is later then the new limb 

 is smaller than its fellow. A limb so reduced in size can hardly be 

 called teratological ; it is a normal development from normal germ- 

 plasm, the germ-plasm reserved from which to develop again lost 

 parts. The same must be essentially true of the wings. 



In the Lepidoptera we are much more familiar with the absence 

 of a wing, or its being of small size, than with the same phenomenon 

 when it affects the legs. This is certainly not because the wings are 

 more liable to such defects, but, no doubt, because practically all the 

 wings of every Lepidopteron preserved are scrutinised, whilst the 

 legs of not one in ten thousand, or perhaps one hundred thousand, 

 are looked at, the fore-legs in some degree excepted. 



There can be little doubt that such cases are generally the 

 normal results of regeneration, and are not, therefore, teratological, 

 but it is nevertheless indisputable that unless we have the life- 

 history of the specimen it cannot be asserted in any particular case 

 that the deficiency is not teratological, has nothing to do with ampu- 

 tation and regeneration, but dates from some defect of the original 

 germ-plasm of the individual. 



This is still more the case when we come to such things as 

 reduplicated or triplicated appendages. It is impossible to say 



