28 GENERAL EMBRYOLOGY 



another kind, that is to say, the problem of heredity, may be 

 more clearly understood by recognizing that the characteristics 

 of the organism are specific at all stages of its existence. The 

 egg of the star-fish is just as much a star-fish as the adult is. The 

 germinal substance of successive generations of star-fish is 

 directly continuous. This continuity of specific organization 

 through the germ, combined with essentially uniform conditions 

 of development, determines the essential uniformity of each 

 series of interactions leading to the formation of a new adult 

 organism. In a real sense the problem of heredity thus becomes 

 the same as the problem of development. And the problem 

 why the egg of the star-fish develops into a star-fish and not 

 into a sea-urchin, is fundamentally the same as the problem 

 why the star-fish is not a sea-urchin; it is the general problem 

 of the evolution of organic diversity. 



REFERENCES TO LITERATURE 



In the "references to literature," given at the end of each chapter, 

 the author's name and the title of the work, are followed by the reference 

 to the journal in which the work appeared, or to the place of publication, 

 in case the work is a separate publication. The number of the volume 

 (Band, tome, etc.) is printed in black-face Arabic numerals, followed 

 by the year of appearance. References to pages, parts, etc., are omitted 

 except in a few necessary instances. 



The abbreviations of the more common references are as follows : 

 Amer. Jour. Anat. American Journal of Anatomy. Baltimore and 



Philadelphia. 



Amer. Jour. Physiol. American Journal of Physiology. Boston. 

 Amer. Nat. American Naturalist. Boston and New York. 

 Anat. Anz. Anatomischer Anzeiger. Jena. 

 Anat. Hefte. Anatomische Hefte. Wiesbaden. 



Arch. Anat. u. Entw. Archiv fur Anatomie und Entwicklungsgesclnchte. 

 Arch. Anat. u. Phys. Archiv fur Anatomie und Physiologic. Leipzig. 

 Arch. Biol. Archives de Biologie. Leipzig and Paris. 

 Arch. Entw.-Mech. Archiv fur Entwickelungsmechanik der Organismen. 



Leipzig. 

 Arch, gesamte Physiol. Archiv fiir die gesamte Physiologic des Menschen 



und der Tiere. Bonn. 

 Arch. mikr. Anat. Archiv fiir mikroscopische Anatomie und Entwicke- 



lungsgeschichte . Bonn. 



