Dr. Holló Ferenc - Dr. Murai Éva szerk.: Parasitologia Hungarica 5. (Budapest, 1972)

More than 90 per cent of the eggs fall between sizes 116-162 x x 60-80 jo,, the practical egg size of P. daubneyi. Eggs deposited by the. individual worms have a relatively constant size. It occured in a high per cent that the measured eggs /60 pes each/ were of the same size, in some other cases smaller and greater 25 p. No direct connexion appears to exist between tne body size of the worm; arid that of the eggs. Table 2 shows the comparison of the body size of ten worms and ten each of their deposited eggs. The eggs are covered with a thin, colourless envelope; its material is /histochemically/ a keratinized selenoprotein /MADHAVI

, 1966/. It forms in the proximal part of the uterus, from the enveloping substance of vitelline cells. Surveys of serial sections show that the vitelline cells in the ootype are full of envelope grains, and that after arrival in the uterus they encircle the oocyte and form the primary envelope of the egg by their secreting activity /photo 1/. This envelope is of different thickness, with a rough surface, in some places broken through by gaps. The operculum and the envelope join along a finely dentate surface. At the hatching of the miracidium, the operculum generally does not separate completely from the envelope /photo 15/. The operculum is biseriate, the inner layer of the envelope is not contiguous at the operculum. The oocyte is surrounded with numerous /45-65/ vitelline cells of irregular form; their cytoplasm contains glycogen after the formation on the egg envelope /photo 3

/. They measure 25x20 /v, the diameter of the centrally situated nuclei is 4-6 yu. Embryo-formation The process of embryo-formation, the changes enacted in the egg, and the development of some miracidial cells and orgiiini