1898.] 



APPENDAGES IN THE AETHEOPODA. 



937 



there is difficulty in making vei'V accurate measurements of the 

 shorter intermediate joints ; but from a consideration of the 

 individual instances from which the means in Table C were 

 obtained, it is believed that the data are sufficiently reliable to 

 justify what has been said above. It has, moreover, been ascer- 

 tained that the results are the same when the two sexes are 

 considered separately, as the differences between male and female 

 in the ratios o£ the several tarsal joints to the whole tarsus are 

 extremely slight, so that the figures tell the same tale w'hether the 

 two sexes are taken together or separately. 



(c) The Armature of the Tarsal Joints. 



Subject to specific differences the tarsal joints in Blattidae are 

 provided with a closely-set armature of spines. In addition to 

 the numerous small spines all the joints except the terminal one 

 bear at their distal ends strong spurs or calcares, which are 

 directed ventralwards and outwardly, one on either side. Similar 

 spurs are developed in reproduced tarsi. Examination showed 

 that in both kinds of tarsi the armature is sometimes abnormal. 

 The abnormal conditions met with fall under three heads, as 

 follows : — 



(a) A tarsal joint had more than two spurs. In such cases 

 the commonest condition was the presence of one 

 supernumerary spur on one side. 

 (6) A tarsal joint had one of the normal spurs completely 

 absent (there being no scar indicating accidental breaking 

 off). 

 (c) A tarsal joint had a spur of normal form placed some 

 distance anteriorly to the proper position at the end of 

 the joint. 



The following Table shows the incidence of abnormality 

 observed : — 



Table D. 



Peoc. Zool. Soc— 1898, No. LXII. 



62 



