CONTENTS OF VOLUME IX. 



No. 1. — A Preliminary Study of the Causes of Bald-headed Kelp. 



Plate I R. Peters. 



2. — A List of the Described Species of Fossil Amphibia. 



R. L. Moodie. 



3. — On the Anatomy of Grindelia squarrosa. Plates II-VII. 



Nora E. Dalbey. 



4. — A Study of the Histological Variations of Quercus muhlen- 



bergii. Plates VIII-XV John A. Elliott 



5. — A Comparative Anatomical Study of Some Species of 



Xanthium. Plates XVI-XXII Nora E. Dalbey. 



6. — On Cubic Surfaces and Their Nodes S. Lefschetz. 



7. — A Contribution to the Subject of the Factors Concerned 



in Soil Productivity. Plates XXIII-XXVII Con Hoffman. 



8. — Some Methods of Embryological Technique. . . Bennett M. Allen. 



9. — Wax Reconstructions of the Brain of an Embryo Lizard, 



Eumeces. Plates XXVIII-XXXI Clarence L. Turner. 



10. — A Study of the Dimensions of the Chromosomes of the 



Somatic Cells of Ambystoma. Plate XXXII. . James B. Mack. 



11. — The Number of Spermatozoa in Relation to the Sertoli 



Cells Florence Hague. 



12. — Studies upon the Number of Germ Cells in Certain Fishes. 



Cora Downs, and Nellie Taylor. 



13. — A Preliminary Report on the Infusoria of Kansas. Plates 



XXXIII-XLIX Inez Smith. 



14. — The Development of a Tunicate without Nerves. . . . Ida H. Hyde. 



15. — The Influence of Light on Reproduction in Vorticella. 



Ida H. Hyde, and Christine Spreier. 



16. — Some Methods of Studying Fossil Amphibia Embedded in 



Coal. Plate L Roy L. Moodie. 



17. — The Effect of Physical Fatigue on Mental Efficiency. 



Floyd Carlton Dockery. 



18. — A Study of the Germ Cells of Corymorpha palma. Plates 



LI-LIII Lucie M. March. 



19. — Histology of Malva rotundifolia. Plates LIV-LIX. 



Grace McCrone. 



20. — Differentiation of the Oaks by Histological Methods. Plates 



LX-LXIV F. W. Mulsotv. 



21. — Anatomy of Platanus occidetalis. Plates LXV-LXXVI. 



Maude Baird. 



