One of the key hydrodynamic problems of gravitational flow with free surface namely the problem of free or unknown boundary has been dealt with in this study. By means of analytical transformation from N-dimensional space to N-1 dimensional space the equations of movement on the fluid boundary are derived from the Euler´s equations independently of the circumstance, whether this boundary is solid, i. e. the bottom, or free surface. In the second part the boundary potential and closing up the system of boundary equations will be treated. and Štúdia sa zaoberá jedným z kľúčových problémov gravitačného prúdenia s voľnou hladinou - problémom neznámej pohyblivej hranice. Známe sú dve približné riešenia tohto problému. Jedno poskytuje lineárna teória malých rozruchov (malých vĺn) a druhé teória plytkej vody. V štúdii je riešený tento problém priamou transformáciou Eulerových rovníc na materiálové hranice pohybujúcej sa tekutiny, t.j. na pevné steny a na voľnú hladinu. Použitý teoretický prístup sa zaobíde teda bez zjednodušujúcich predpokladov teórie malých vĺn a teórie plytkej vody.
Heliocotyle ewingi sp. n. (Monogenea: Monocotylidae) is described from the gills of Myliobatis australis Macleay, 1881 (Myliobatididae) collected from Norfolk Bay near Hobart, Tasmania, Australia. Heliocotyle ewingi can be distinguished readily from the only other species in the genus, Heliocotyle kartasi Neifar, Euzet et Ben Hassine, 1999, by the presence of a single pseudoseptum on each of the peripheral loculi except the posteriormost, eyespots and by the morphology of the male copulatory organ which is a short, straight sclerotised tube which lacks a sclerotised accessory piece. The generic diagnosis is revised to accommodate the new species and the anterior glands are discussed.