Royal Microscopical Society. 155 



Let me now return to the question of the structure of the 

 Podura scale. I began my investigation on the shde of Degeeria 

 Nigro-maculata sent by Mr. Mclntire. The markings on these 

 scales were very bold, and the object was in every way a beautiful 

 one. As I first arranged the illumination the markings resembled 

 the notes of exclamation as seen on the ordinary test Podura, less 

 rounded at the heads, however, less pointed at the opposite extremity 

 of each marking, and the whole marked obliquely across by a delicate 

 series of transverse lines which were observed most distinctly 

 between the notes of exclamation, but which could readily be made 

 to appear to cover these also, when the fine adjustment was toyed 

 with. I soon found, however, that by proper management of the 

 illumination it was easy to make an appearance " start into view " 

 which recalled at once the descriptions of Dr. Pigott, and Fig. 7 of 

 Plate XXXIII. accompanying his paper of December, 1869. In 

 that paper, it will be remembered, he asserted that the notes of 

 exclamation are mere optical effects produced by two sets of 

 beads arranged in " rouleaus" which cross each other at a small 

 angle. 



He says, of the beads on the surface of the scale nearest the 

 observer : — " But with 2300 diameters they appear to he on the 

 same plane and terminate abruptly on the basic membrane : upon 

 focussing for the strings of beads attached to the lower side, the 

 beading appears in the intercostal spaces. The upper beads are best 

 seen either green upon a pink ground or pink upon a greenish 

 ground." And farther on : — " By estimation, comparing these beads 

 with those of the P. Formosum of ^wooth inch in diameter, the 

 observed Podura beads may be reckoned at siy^oth to xroVo o^h of 

 an inch in diameter. The spines usually drawn really embrace in 

 general three or four beads." 



I understood, at the time, the foregoing description to be intended 

 for the scales of Lepidocyrtus curvicolUs, and this opinion is con- 

 firmed by the remarks of Dr. Pigott in a subsequent paper ;* but 

 from the statement of Mr. Mclntire that the Podura scale exhibited 

 by Dr. Pigott to the Microscopical Society was really a scale of 

 Macro toma,t I presume that the coarser scales aided him in 

 arriving at his interpretation of the structure of Lepidocyrtus. In 

 any event, in his paper published in January, 1870, the same 

 structure is predicated of Macrotoma and Degeeria domestica, the 

 scales of which are said to " render that easy which is exceedingly 

 difficult in the regular test scale." We are further told, in the same 

 paper, of the Degeeria, — " A lady who is now viewing the scale says, 

 ' the beads look just like rows of peas in a pod.' "J 



The description given by Dr. Pigott in his first paper, as quoted 



* ' Monthly Microscopical Journal,' vol. iv., p. 305. j lb., vol. v., p. 12. 



X lb., vol. iii., p. 13. 



