Conversation so far:
Where was Sigmund Freud born?
Sigismund Schlomo Freud was born to Jewish parents in the Moravian town of Freiberg, in the Austrian Empire.
When was Sigmund Freud born?
Sigismund Schlomo Freud was born on 6 May 1856.
Where did Sigmund Freud go to school?
In 1865, the nine-year-old Sigmund Freud entered the Leopoldstädter Kommunal-Realgymnasium, a prominent high school.
What did Sigmund Freud study?
Sigmund Freud loved literature and was proficient in German, French, Italian, Spanish, English, Hebrew, Latin and Greek.
When did Sigmund Freud graduate?
Sigmund Freud proved to be an outstanding pupil and graduated from the Matura in 1873 with honors.
Did Sigmund Freud study anywhere else than the Leopoldstädter Kommunal-Realgymnasium?
Sigmund Freud entered the University of Vienna at age 17. He joined the medical faculty at the university.
Did Sigmund Freud do research anywhere else other than the University of Vienna?
In 1876, Sigmund Freud spent four weeks at Claus's zoological research station in Trieste, dissecting hundreds of eels in an inconclusive search for their male reproductive organs.

Question: What did he do research on?
Self-contained rewrite: What did Sigmund Freud do for zoological research?