EN
The aim of this work was to show to what a degree the extracts of the various species of lichens can change the normal process of development of the eggs. For preparing the extracts from lichens solutions of various pH were used : 0.1 N Hcl. 0,1 N NaOH, H2O-distill., buffer pH-7,2 and physiological salt. Mature eggs isolated from the uterus of Ascaris suum were used. The eggs with the extracts were kept in a thermostat at 26°C for 46 days. During the culture. the dynamics of the development of the eggs was traced, particularly the changes of the internal and external structures were observed, that is the damage of the membranes, granulation and vacuolization o the cytoplasm, the mass of the yolk and other phenomena. The observations of the eggs were carried out at 2-3 days intervals. The development of the eggs of Ascaris in the lichen extract does not run a continuous course, it depends on the species of the lichen used and on the pH of the cxtract. Acid extract offer conditions nearly optimal with the exception of the lichen Xantoria parietina, where the development of the blastuli in the culture was inhibited. Alkali, water and buffer extracts slow down the ovostatical activity or prolong the time of the development of the eggs of Ascaris. The damaging (ovocidal activity) of the extracts is not high and it might not be taken into consideration. The results of these observations are shown in the table 1.