Before sailing for Europe on *April 8. Pablo Casals, the distinguished cellist, will make his debut ip America as a symphony conductor on April 7, at Carnegie hall with a special orchestra recruited in TCew York. Mr* Casals has conducted symphonic concerts since he was 20 years old, not only In Spain but at the Lamoureaux concerts in Paris and also in South America. Recently he founded his own orchestra in Barcelona, the official title being “Orquestra Pan Casals/' He has already given three seasons concerts in Barcelona.Walter Damrosch began ?». second