318 THE A3IBRICAN MONTHLY .v^v 



dance ou the rocks by the shore at Lynmoutli, in North 

 Devon. The scales are to my mind prettier than those 

 of Lepisraa on account of the regularity of their trans- 

 verse striae, which are absent from the latter. On the 

 other hand, tliis one has not the radiating marks of Le- 

 pisma, though both structures occur in Tomocerus. 



Lepisma sacchariua. — This insect is pressed down on a 

 slide instead of the cover. The scales are transferred to 

 a slip of glass, generally the cover-glass, by simply press- 

 ing it gently on the body of the insect. And the scales 

 have that side uppermost which was nearest the body. In 

 another slide the scales were pressed down ou the cover, 

 and so the uppermost side is the outermost, when the 

 scales were on the insect. It will be seen that the longi- 

 tudinal marks are on the outer side, and the radial ones 

 on the side next the body. 



Mr. Joseph Beck, in an appendix to Sir John Lubbock's 

 "Monograph of the CoUembola and Thysanura," states 

 that the longitudinal markings are on the under side of 

 the scale, whilst the outer side bears the radial markings 

 or corrugations. 



Mr. R. Beck further pointed out that the crossingof these 

 two sets of markings produced a curious optical effect. 

 At the extremity of the scale where the markings cross 

 each other very obliquely a series of "exclamation marks" 

 like those of Podura is produced ; but where, as at the 

 sides, the crossings are^nearly at right angles, the mark- 

 ings appear like rows of beads. 



This optical effect is still more strikingly shown and 

 represents two scales of Polyommatus argiis lying partly 

 over each other, and producing an appearance very simi- 

 lar to that of a coarse Podura scale. Of course, the mark- 

 ings which are uppermost appear continuous, and t])ese 

 are the longitudinal marks where the outer surface has 

 been pressed against, the cover. The presence of a little 

 grease on the slide also serves to point to the same conclu- 



