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aspect of the field in which they work and all later growth is influenced by their labors."

The greatest classic in embryology is his 'Entwickelungsgeschichte der Tiere—Beobachtung und Reflexion,' the first part of which was published in 1828, and the work on the second part completed in 1834, although it was not published till 1837. This second part was never finished according to the plan of Von Baer, but was issued by his publisher, after vainly wailing for the finished manuscript. The final portion, which Von Baer had withheld, in order to perfect in some particulars, was published in 1888, after his death, but in the form in which he had left it in 1834.