Morphology and histochemistry of the oviduct and egg‐jelly layers in the frog, <i>Rana pipiens</i>

Abstract Morphologically the oviduct of the frog, Rana pipiens , consists of a lining epithelium and tubular jelly‐secreting glands. The oviduct can be divided into six regions (designated R1 anteriorly—R6 posteriorly) based on the differential staining of the jelly glands. The regions measured 1, 5, 6, 3, 20 and 3 cm, respectively. These regions correspond to 6 histochemically distinct layers of jelly (designated J1 nearest the egg through J6 farthest from the egg) which are deposited around the egg during the egg's sojourn in the oviduct. A correlation between lengths of each oviducal region and thickness of individual jelly layers was observed. That is, J5 is the thickest, followed by J3, 2, 6, 4 and J1 which is thinnest. Histochemical properties of jelly glands and corresponding jelly layers were essentially the same in the tests performed. All regions and layers except R5 and J5 contain a large amount of acid mucopolysaccharide and the mucopolysaccharide in R and J1, 3 and 4 is sulfated. Neutral mucopolysaccharide is present in R2, J2, R5 and J5. Although protein is present in all layers and oviducal regions it was found in higher concentration in R and J1, 3 and 6 and in lowest concentration in R and J2.