"Her funeral service was even held in the building.
"Margaret was a very well-loved figure in Wellington and her generous legacy will benefit future generations of animal lovers."
Doucas was principal barrister and solicitor with Henry Hughes, Patent & Trademark Attorneys.
She was one of the first women in New Zealand to hold both science and law degrees and to be a qualified lawyer and patent attorney.
She didn't speak a word of English when she started school but she graduated from high school at the top of the class.
Her bequest to the SPCA was on top of significant financial donations made during many decades of service with the charity. She had started as a volunteer at the age of 5.
The money has also allowed the Wellington SPCA to launch the 'Home Ever After' initiative which helps in the care of animals after the owners have died.
"It is a pretty incredible legacy Margaret has left for the community," Gattung said. "Anyone who knew her knew how vibrant she was.
"She was bright, compassionate and a trailblazer in her professional life."
"Her generosity will benefit not just people in the Wellington area as our centre will be used for national events and forums. It is a fantastic building."
Gattung added that despite the large bequest, there was still a need for ongoing donations to the organisation.