INSECTA. 



Cll 



dinal and trausverse striae, which should be clearly defined, 

 and the spots separated : this is a good test of the defining 

 power of a quarter-inch object-glass. 



No. 3, Hipparchia janira, Common Meadow Brown 

 Butterfly scale : on this we see a number of brown spots 

 of irregular shape and longitudinal striae. 



No. 4, Pontia brassica, Cabbage-butterfly, affords an 

 excellent criterion of the penetration and definition of a 

 microscope : it is provided at its free extremity with a 

 brush-like appendage. With a high power, the longitu- 

 dinal markings appear like rows of little beads. Cheva- 

 lier's test-object is the scale of the Pontia brassica, the 

 granules of which must be rendered distinct. Mohl and 

 Schacht use Hipparchia janira as a test for .penetration, 

 with a moderate angular aperture and oblique illumina- 

 tion. Amici's te^t-object is Navicula Rhomboides, the dis- 

 play of the lines forming the test; this is a very good test 

 for angular aperture. 



Fig.27is. — Portions of Scales, magnified 500 diameters. 

 la, Portion of Scale of Morpho Menelaut. 5a, Portion of Large Scale of Podura 

 Plumbea. 7, Scale from the Wing of Gnat; its two layers are here represented. 

 8, Portion of a Large Scale of Lepisma Saccharina. 



The Tinea vestianella, Clothes-moth, possesses very deli- 

 cate and unique scales ; two of these are imperfectly 

 represented near the Acarus taken from one of these moths, 

 uf, p&fta G41. The feathers from the under-side of the 



it R 2 



