37 
dorsal series invariably ranged to the first segment in front, and to the 
eleventh and twelfth segments behind. The spots or a certain spot on 
one side of the body may often be decidedly larger than those of the 
other side; furthermore they may be present on one side only, — the 
spots are in this way not always symmetrical in occurrence. 
The actual cause of the variation above stated is not known to 
me at present. The occurrence of spots shows, it appears to me, not se- 
condary sexual character, as I have found spotted as well as non-spotted 
individuals may occur among the both sexes. On the other hand, a ra- 
cial difference seemingly exists with respect to the spot-character. On the 
pernyan larvae hatched out from the newly imported eggs from China, 
the bright spots were found more developed than in our native race. 
The hereditary behaviour of the spot character, will, therefore, interrest- 
ing to be made out. 
As early as the first stage of the larval life there is detected no trace 
of the spots; they come into view only in the second stage, and are added 
hence forward by each succeeding moult in their dimension, as well as, 
as it occasionally happens, in their number. 
Microscopical observations can be made in the following way. 
Pieces of the cuticle are cut off in such a way as to contain in each piece 
a bright spot and its surrounding parts, while anything adhered to their 
inner surface is cleaned off. Under a low power these two parts, the 
spots and its environs, reveal some characteristic differences. Seen in 
transmitted light, the cuticle is, in the region of the bright spot, almost 
transparent, only slightly coloured, and is quite smooth on its free sur- 
face; in the surrounding parts it differs from that of the spot, not only 
in being semitransparent, but in showing a somewhat conspicuous colour 
of yellowish green. In this latter part the cuticular surface is not 
smooth, but is, as in the other parts of the general body-covering, pro- 
duced into numerous papillae which are thickly covered with minute 
hairs; and between these papillae, there are in addition large club- 
shaped papillae and long stout bristles. 
On the series of sections into which the pieces were divided, more 
detailed structure are made out. The cuticle of the spot is, as the sec- 
tions show, composed of two distinct layers, the outer and the inner. 
The outer layer is about 10 « in thickness and homogeneous in structure, 
while the inner layer is as several times thick as the outer, and shows, 
through its whole thickness, a great number of fine striations running 
parallel to the surface. In the surrounding parts, on the other hand, the 
cuticle is thicker than the inner and outer layers of the spot taken tog- 
ether, and is characterized by its homogenous structure. Though, as it 
often happens when the knife edge is not finely sharp enough, the homo- 
