Which scientific subjects did Louis Agassiz investigate in the United States?

During his time in the United States, Louis Agassiz primarily investigated the following scientific subjects:

• Natural History and Geology: Upon arriving in 1846, Agassiz traveled to study these fields generally, eventually accepting a professorship of zoology at Harvard University in 1847.1
• Ichthyology: He continued his research on fishes, publishing numerous papers on the subject, including a notable study on the viviparous surf fishes of California.1
• Embryology: His research included significant work on the embryology of turtles, featured in his four-volume Contributions to the Natural History of the United States.1
• Glaciology: Expanding on his earlier European research, Agassiz found additional evidence for an ice age while in North America.2
• Classification: He published the Essay on Classification (1859), which reflected his theoretical views on the organization of the natural world.1

Agassiz also worked to establish a comprehensive museum for zoological research at Harvard, which became the Museum of Comparative Zoology.1