38 
geneous cutends of sections show a fracture which is peeled off; in this 
way we can see that the direction of cleavages is never parallel to the 
cuticle surface. 
The cuticle of the spot as well as that of the surrounding parts show 
almost equal staining affinity against haematoxyline. On the other hand 
congo-red, ruby, acid-green, etc. stain the cuticle of the spot more inten- 
sely than that of the other parts. This latter series of the staining fluids 
is therefore to be utilized for staining differentiation of the two parts 
under consideration. I can not say at present with certainty whether 
this staining distinction between these two parts is due to certain che- 
mical differences of one from the other, or merely physical difference in 
structure. 
Although quite free from the large processes, the cuticular surface 
of the spot is sometimes provided with numerous papillae, which are 
nearly equal in size with one another, and are so minute that they have 
no effect upon the brightness of the spot. The inner layer of the 
cuticle is composed of a large number of thin lamellae laid in layers 
parallel of the surface, and owing to this lamellar structure, an appear- 
ance of fibrous striations is always revealed on sections passed through 
in any given directions. A single lamella is sometimes not broad enough 
to cover a bright spot to which it belongs, but several lamellae compose 
a lamellar layer, overlapping on each other at their edges. 
All the subcuticular elements, such as the epidermic cells, tracheal 
tubes, musculature, etc. which underlie the cuticular coat, are not parti- 
cular to the part of bright spot, but are by no means discernable from 
those in other part. 
The metallic lustre is undoubtedly produced by reflection of light 
which takes place at the surface and within the structure of the spot 
cuticle. The colour of spot is due partly to the »dermal (cuticular) 
colour« (as called by Hagen) of the spot and the interference colour 
which can be possibly assumed to result from the layered structure 
of the spot, and partly to the pigment contained in the epidermic 
cells. To attest the polarizing power of the spot-cuticle, I made use of 
polarization-microscope; but the result was negative. 
In both the species of the Oak-silkworms and in both the lateral 
and dorsal series, the spot presents during a few hours after an ecdysis 
a colour all alike, i. e. milky white, closely resembling a piece of white 
porcelain. But the spots soon assume colours according varying the 
species as well as positions. In A. yamamai, all bright spots are almost 
silvery white, while in A. pernyi the spots of the dorsal series are golden 
yellow, and those of the lateral series are copper-red in colour. The 
colour divergence above mentioned is possibly due to the difference 
