ACKNOWLEDGMENTS 



Acknowledgment is due and hereby gratefully made to the 

 following, for permission to reproduce figures : 



Akademische Verlagsgesellschaft m.b.H., Leipzig (Verh. d. 

 Deutsche!' Zool. Gesells., Zeitschrift f. wissenschaftl. Zoologie)\ 

 Cambridge University Press {Anatomy and the Problem of Be- 

 haviour, Coghill; Biological Reviews) Experimental Cytology, 

 Gray); Chicago University Press {Botanical Gazette \ General 

 Cytology, Cowdry; Individuality in Organisms, Child; Physio- 

 logical Zoology); Columbia University Press {Experimerital 

 Embryology, Morgan); MM. Gaston Doin et Cie, Paris {Archives 

 de Morphologic)', Herren Gustav Fischer, Jena {Allgemeine 

 Biologic, Verh. d. Afiatomischen Gesells., Zoologische Jahrbikher); 

 Messrs Henry Holt & Co., U.S.A. {Physiological Foundations of 

 Behavior, Child); The Lancaster Press, Inc., U.S.A. {Biological 

 Bulletin); The Marine Biological Laboratory, Woods Hole, 

 Mass., U.S.A. {The Biological Bulletin); Messrs Methuen & Co., 

 Ltd. {Problems of Relative Growth, Huxley); Le Museum d'His- 

 toire Naturelle, Geneve {Revue Suisse de Zoologie); National 

 Academy of Sciences, Washington, U.S.A. {Proceedings); Oxford 

 University Press {Introduction to Experimental Embryology, 

 de Beer; Experimental Embryology , Jenkinson; Quarterly Journal 

 of Microscopical Science); The Council of the Royal Society, 

 London {Proceedings, Philosophical Transactions); The Science 

 Press, U.S.A. {The American Naturalist); Herren Julius Springer, 

 Berlin {Archiv f. Entwicklungsmech. d. Organismen, Archiv f. 

 Mikros. Anat. u. Entwicklungsmech., Naturwissenschaften, Ergeb- 

 nisse d. Biologic, Ha?idb. d. norm. u. pathol. Physiol., Zeitschrift 

 f. vergleich. Physiol.); Herr Georg Thieme, heipzig {Biologisches 

 Zentralblatt); The Waverley Press {The Science of Life, Wells, 

 Huxley and Wells); The Waverley Press, Inc., U.S.A. {Journal 

 of Experimental Medicine); The WiHiams and Wilkins Company, 

 U.S.A. {Quarterly Review of Biology); The Wistar Institute of 

 Anatomy and Biology, U.S.A. {Journal of Experimental Zoology). 



Acknowledgment to the authors of the works from which 

 these illustrations are taken is made in the legends. 



