Semithin and in particular ultrathin sections of the glandular subdivisions in the oviduct of the terrestrial egg laying, direct developing plethodontid salamanders Bolitoglossa pesruba and Oedipina uniformis revealed remarkable structural differences of secretory products between the two species and in B. pesrubra between the different subdivisions of the duct. In the latter species structure of the secretory granules confirmed the previously described histological differentiation of the glandular portion of the oviduct in four subdivisions. In the first subdivision most secretory granules were moderately electron-dense having a distinct osmiophilic core, in the second these cores are absent, in the third granules revealed a complex inner structure and in the fourth they are more or less homogeneous and electron dense. In O. uniformis, however, secretory granules were differently stained in semithin sections with toluidine blue, but showed a homogeneous moderately electron-dense appearance along the entire oviduct. As oviductal secretions form the generally multi-layered glycoproteinaceous egg jelly enveloping the ovum when passing down the oviduct, our results suggest that in terrestrial breeders considerable differences exist in these secretions even at the structural level and, therefore, very likely in number and nature of egg jelly layers.
The fine structure of the oviduct, oviduct-uterine junction and uterus of the nematode Toxocara canis (Werner, 1782) is described. Columnar-type epithelioid cells with numerous microvilli at the apical membrane border the oviduct lumen. Many electron dense secretory products are present in these cells. The cells lining the oviduct-uterine junction have no microvilli. They are coated with an electron-dense layer and contain numerous membrane-bound dense material containing bodies. Externally, the cells are surrounded by a basal lamina and muscle cells. The epithelial cells lining the greater part of the paired uteri appear to be rather flat. The oocytes inside the oviduct are covered with a dense thick plasma membrane and contain lipid droplets, dense granules and glycogen. The morphology of the oocytes before the fertilization inside the oviduct-uterine junction resembles that of the oocyte in the oviduct. After the fertilization the egg shell formation takes place. The egg shell of T.canis is composed of four layers: uterine, vitelline, middle chitinous and inner layer. The differences between the fine structure of the egg shell of T. canis and other related nematodes are discussed.