232 
EDWARD A. MINCHIN. 
the older stages at all events, to consist here of two layers 
everywhere except where the cuticle is folded to form an arti- 
culation ; in these parts only the upper layer remains. In 
certain places the cells of the lower layer become giant-cells 
(g. c.), which have large nuclei and very granular cell contents, 
and are provided with processes, and are without doubt ganglion- 
cells. They are scattered over each tergum, but are extremely 
abundant in the fore part of the tergum, i. e. that part which 
is overlapped by the tergum next in front, where they form an 
almost continuous layer. Hence it does not seem possible 
that they should always correspond with hairs. If a Cock- 
roach be dissected in strong spirit, these cells can be seen 
with a low power forming irregular brownish patches in the 
fore part of each tergum, and with care they can be scraped 
off and floated on to a slide and stained and mounted in situ, 
when they present the appearance shown in fig. 5. They are 
large irregular cells, more or less overlapping one another and 
provided with processes, usually two or three. Between them 
are seen ordinary nucleated cells of the lower layer of the 
hypodermis, with which they are continuous. Fig. 6 shows a 
single one of these giant-cells. Though most numerous in the 
fore part of each tergum, they are also found scattered through- 
out its whole extent. 
Hence I believe the hypodermis (fig. 7) to have the following 
structure : an upper regular layer of cells, which corresponds 
to the polygonal areas of the cuticle, and is continuous through- 
out the body, and is continued on to the tracheae ; and a 
lower, very irregular layer, which occasionally seems to form 
two layers, and is wanting where the cuticle is folded to form 
an articulation, and the cells of which are in places directly 
modified into nerve-end cells. These nerve-end cells are prob- 
ably connected with a seta where the terga are exposed, but 
where they are overlapped seem merely to be connected with 
small papillae. Below these two layers is placed the basement 
membrane ( b . to.), which is apparently a thin, homogeneous 
membrane. 
My investigations were carried on in the Morphological 
