chap. xv.] antennae: earwigs. 415 



though the 13-jointed antenna is not as a whole so long as the 

 14-jointed antenna of the same individual it is longer than its 

 first 13 joints. 



But besides the common 13-jointed form occasional specimens 

 are as shewn in Fig. 124, II. Here both antennas are 13-jointed, 

 the 3rd joint being much longer, and the 4th a little longer than 

 the corresponding joints of the normal with 14 joints. Two 

 specimens were seen having this structure in both antenna?, thus 

 presenting a difference which, did it occur in a form known from 

 but few specimens, would assuredly be held to be of classificatory 

 importance. 



In another case (Fig. 124, III) each antenna contained only 

 12 joints, the 3rd, 4th and oth being all of greater length than 

 in the normal. 



Fig. 124, IV shews a case in which there was on the right 

 side a normally 14-jointed antenna but that of the left side was 

 12-jointed, agreeing nearly with those in Fig. 124, III. 



In considering these facts the possibility that some or all the 

 abnormal states may result from or be connected with regenera- 

 tion must be remembered ; but from the frequency of the varia- 

 tions, from their diversity, and from the fact that symmetrically 

 varying individuals are not rare, it is on the whole unlikely that 

 all can owe their origin to regeneration. It will besides be 

 noticed that it is in the proximal joints that the greatest changes 

 are seen, and it must surely be rarely that these are lost by mutila- 

 tion. 



The difficulty — indeed the futility — of attempting to adjust a 

 scheme of individuality among such series of segments must here 

 be apparent to all. We can see the change in number and the 

 change in proportions, and we are doubtless entitled to affirm 

 that the differences between these several kinds of antennas are 

 reached by changes occurring chiefly in the neighbourhood of 

 the 3rd and 4th joints; but not only is there no proof that the 

 changes are restricted to these joints, but the appearances suggest 

 that there are correlated changes in many, and perhaps in all of 

 the joints. 



Tarsus of Blatta 1 . 



25. Among the families of the class Orthoptera the number of 

 tarsal joints differ. In Forficularia the number of tarsal joints 



1 In connexion with variation in the number of joints in legs I may mention the 

 case of Stenopterus rufus ? (Longicorn) described by Gadeau de Kebville as having 

 each tibia divided into two parts by an articulation (Le Naturaliste, 1889, s. 2, xi. 

 p. 9, Jig.) ; but upon examination it proved that each tibia had been sharply bent at 

 each of these points, and there was no real articulation. I have to thank M. Gadeau 

 de Eerville for lending me this insect together with many interesting specimens of 

 which mention will be made hereafter. 



