160 THE AMERICAN NATURALIST: [Vou. XXXII. 
suggested the subject and laid out the plan of study, witha 
minor portion really contributed by the student himself. 
Agassiz may have left his students too much to themselves, 
but he had what most teachers do not possess, — the power of 
leading his students to take broad views of a subject. As a 
teacher, then, Agassiz was broad and philosophical, and his 
pupils were constantly urged to add to their special work on 
the anatomy or embryology of some animal a wider knowledge 
of the relations of the animal itself to its allies and to the world 
it lived in, and more particularly to its fossil allies. 
Philosophy inquires into the causes and meaning of things, 
philosophy thinks and speculates, and philosophy is nothing 
unless comparative in its methods. Agassiz was in season and 
out of season urging us to think at every stage of our investiga- 
tion, to inquire what is the meaning of this or that feature or 
change in organs during growth, and at every step we were 
told to compare. His earliest lectures, delivered to popular 
audiences, soon after his arrival in this country were on ‘‘Com- 
parative Embryology.” The great museum he founded was the 
Museum of Comparative Zoology. Whatever he wrote or when- 
ever he spoke his ideas were large, synthetic, and philosophical. 
It was these magnificent qualities, together with his undying 
enthusiasm, which made Agassiz one of the greatest of teachers 
in that line of great teachers of modern biology whose intellectual 
parents were Ddllinger and Von Baer. 
‘From Agassiz as a philosophical teacher let us turn to his 
work as an investigator, and inquire whether philosophic, 
synthetic methods were here employed by him. 
Undoubtedly Agassiz’s most important, far-reaching, and 
permanent contribution to science was the glacial theory. 
At the outset prejudiced against the idea of Venetz and 
of Charpentier as to the former great extent of the Swiss 
glaciers, after personal conversation and discussion with 
the latter geologist he became convinced of his error. He 
spent several summers among the Swiss glaciers, afterwards 
visited Great Britain, observed moraines, studied rocks and 
boulders, and inferred that glaciers had formerly existed in 
Wales and Scotland, that northern Europe had once been 
