ANATOMY AND PHYSIOLOGY I29 
conforms to the general segmentation and is arranged in each 
segment with an approach to'symmetry. Much of this tissue 
forms a distinct peripheral layer in each segment, and masses 
of fat-body occur constantly on each side of the alimentary 
Fic. 163. 
Sts 
TO 
i 
ayn avn 
Transverse section of the abdomen of a caterpillar, Pieris rape. b, blood corpus- 
cles; c, cuticula; d, dorsal vessel; f, fat-body; g, ganglion; h, hypodermis; /, leg; m, 
muscle; mt, mid intestine, containing fragments of cabbage leaves; mt, Malpighian 
tube; s, silk gland; sp, spiracle; tr, trachea. 
tract and also at the sides of the dorsal vessel, in the latter case 
forming the pericardial fat-body. 
Fat-Cells.—The fat-cells (Fig. 164) are large and at first 
more or less spherical, with a single nucleus (though there are 
said to be two in Apis and several in Musca), but the cellular 
10 
