The initial "P." stands for his father's name Prabalanathan, although some sources note it incorrectly as "Peter".
He retired voluntarily in 1929 to become a professional insect collector and natural history dealer.
[2] Although he specialized mainly in insects he also sold mollusc shells across Europe and North America and numerous species have been described on the basis of specimens collected by him, several named after him, including:[3] Alexander named a cranefly Styringomyia susilae after his then infant daughter.
Selva Nathan at the Sugarcane Breeding Institute, Coimbatore) continued the natural history specimen business.
The tiger beetle species Jansenia nathanorum was named for the Nathan family by Fabio Cassola and Karl Werner in 2003.