Today we mark the bicentennial of the birth of Jean Louis Rodolphe Agassiz, one of the premier scientists of his day. Although today he is celebrated as a zoologist, glaciologist, and geologist, he considered himself primarily an ichthyologist.

A zoologist is concerned with the classification, properties, and vital phenomena of animals; a glaciologist studies snow or ice accumulation, glaciation, or glacial epochs; a geologist deals with the history of the earth and its life, especially as recorded in rocks. And then there's the ichthyologist, who works with fishes. (来源：英语图片 http://photo.englishcn.com)

The history of the words zoologist, glaciologist, and geologist are all pretty straightforward. As used here, the noun suffix –ist denotes "one who practices, studies, or specializes in a specified art or science, or in a particular field of knowledge or particular skill." Glaciologist traces to the Latin noun glacies, meaning "ice;" and zoologist and geologist have ancestors in the Greek zoe and ge (meaning "life" and "earth," respectively). Likewise, the ichthy in ichthyologist meant "fish" in Greek. (来源：英语麦当劳－英语快餐EnglishCN.com)