At the same time as the Study Week on Biological and Artificial Membranes and Desalination of Water, the Plenary Session of the Academy was held on 17-19 April 1975 with the participation of 25 Academicians.
The President, Prof. Carlos Chagas, gave a report on the activity carried out during the last three years, commemorated the deceased Academicians, and introduced and presented the insignia to the new Academicians nominated on 24 June 1974 by the Holy Father.
The following scientific communications were presented during the Plenary Session: Chagas, Chaudron, De Almeida, Dirac, Garnham, Herzberg, Lecomte, Lejeune, Lora-Tamayo, Marini-Bettòlo, Mizushima, Picone and Roche.
Three papers were also given. Academician Prof. Marini-Bettòlo commemorated the personality and scientific work of the deceased Academician Prof. Domenico Marotta; Prof. Giampietro Puppi spoke about "The scientific and technical aspects of safeguarding Venice”, and the Academician Prof. Severo Ochoa addressed "The Molecular Basis of Heredity and Evolution".
Finally, Dr. Stephen Hawking, winner of the Pius XI Gold Medal, presented to the Academy a summary of his scientific research, focused especially on the study of the relationship between the forces of gravitation and expansion existing in the universe and the investigation of so-called "black holes".