APA (7th ed.) Citation

Hertwig, O. The Biological Problem of To-day: Preformation Or Epigenesis? The Basis of a Theory of Organic Development.

Chicago Style (17th ed.) Citation

Hertwig, Oscar. The Biological Problem of To-day: Preformation Or Epigenesis? The Basis of a Theory of Organic Development.

MLA (9th ed.) Citation

Hertwig, Oscar. The Biological Problem of To-day: Preformation Or Epigenesis? The Basis of a Theory of Organic Development.

Warning: These citations may not always be 100% accurate.