Printed in Great Britain THE FINE STRUCTURE AND HISTOCHEMISTRY OF THE FAT BODY IN THE LOCUST,

A histochemical study of the fat body attached to the male accessory reproductive glands of the mature desert locust shows that most of the fat body is occupied by neutral fat and probably a little acidic lipid. The cytoplasmic strands between the enormous fat globules contain large deposits of glycogen and some protein. An electron-microscopic study of the mature fat body demonstrates that the synthetic machinery within the cytoplasm is sparse: the endoplasmic reticulum is scarce and in the form of isolated and flattened cisternae; there are few ribosomes; the Golgi units are rather rare and small; and the cytoplasmic bodies, which are thought to be derived from pinocytotic vesicles and probably contain precursors for carbohydrate and lipid synthesis, are few in number. Microtubules, of about 200 A diameter, and each formed as a compact helical structure with a repeating period of about 150 A, are found occasionally in the cytoplasm. Their function is unknown, but they are found closely associated with mitochondria and lipid globules. It is suggested that little synthesis takes place in the mature fat body since there is little nutri-ent circulating in the haemolymph, and that at this stage it acts mainly as a storage organ for glycogen and neutral fat