CHAP, xx.] EXTRA ANTENNAE ARISING TOGETHER. 519 



position the serrated border of the right antenna faces towards 

 the left side, and that of the left is turned towards the right. 

 The structure of the abnormal specimen is as follows. 



Left Antenna. Scape normal. Its plane however is not quite 

 horizontal as usual, but is a little oblique, the anterior border being 

 slightly higher than the posterior. In the funiculus the 1st and 

 2nd joints (2nd and 3rd of the whole antenna) are a little thicker 

 than usual but otherwise normal. The 3rd joint of the scape 

 is enlarged and presents at its apex two sockets, each bearing 

 a continuation as shewn in the figure. The two sockets are not 

 in a horizontal plane, but their plane is oblique and nearly at 

 right angles to the plane of the scape, the socket bearing the 

 branch I 1 being the higher. It is important that the precise re- 

 lations of these parts should be clearly understood. 



This outer socket of the 3rd funicular joint bears the branch I 1 , 

 made up of three more funicular and three club-joints, turning 

 their serrated border in the direction of the right antenna : I 1 is 

 therefore structurally a left antenna. Its surface is of the same 

 nature as that of a normal antenna, but its size is a little smaller. 

 It is in an oblique plane inclined to the horizontal at about 45°, 

 the posterior (outer) border being the higher. 



The inner socket of the 3rd funicular joint bears a cylindrical 

 joint not quite fully segmented off from the next joint peripheral 

 to it. These two are 4th and 5th funiculars. The 5th again 

 presents two sockets, bearing respectively the branches I 2 and 

 I 3 . The branch I 2 has one small joint (6th funicular) and three 

 club-joints, turning their serrated border towards I 1 . This branch 

 is therefore structurally a right antenna. It stands in the same 

 oblique plane as I 1 , the serrated border being the higher. In 

 size it also agrees with I 1 , being rather smaller than the normal. 

 The branch I 3 is a normal left in size and shape, and it lies in 

 a horizontal plane. 



Here therefore there is a left antenna and a pair, one a right 

 and the other a left. Which then is the normal, I 1 or I 3 ? Inas- 

 much as I 3 and I" arise by a common stalk it may seem that 

 they are the extra pair and that I 1 is the normal. We have 

 now seen in many cases that extra parts in Secondary Symmetry 

 are compounded together as l A and I 2 are here. But considering 

 the fact that I 3 is of normal size' and in the normal horizontal 

 plane, whereas l l and P are both smaller and are in an oblique 

 plane complementary to each other, I incline to the view that 

 if one branch is the normal, it is I s , and that I 1 and I- are the 

 extra pair in Secondary Symmetry, though they do not arise to- 

 gether. They are then nearly in Position DPP, but depart from 

 that position in the fact that I 1 is not horizontal (cp. No. 757). 



If l l and P are really the extra parts, in the fact that they 

 do not arise together, but spring separately from different points 

 on the normal, we meet with a condition rarely seen, but that 



