IV CONTEXTS. 



No. 4. OCTOBER, 1919. 



RICHARDS, A., AND GOOD, DONNELL J. Notes on the Effect 



of X-radidtion on the Development of Cuming'ni Eggs . . . 209 



STOCKARD, C. R., AND PAPANICOLAOU, G. N. The Vaginal 

 Closure Membrane, Copulation, and the Vaginal Plug 

 in the Guinea-pig, with Further Considerations of the 

 (Estrous Rhythm 222 



SMITH, BERTRAM G. The Individuality of the Germ-inn lei 

 During the Cleavage of the Egg of Cryptobranchus alle- 

 gheniensis . . 246 



No. 5. NOVEMBER; 1919. 



GARREY, WALTER E. The Nature of the Fertilization Mem- 

 brane of Asterias and Arbacia Eggs 287 



BALDWIN, W. M. The Effect of Ultra-violet Rays upon the 



Development of the Frog's Egg 294 



BELLAMY, A. W. Differential Susceptibility as a Basis for 

 Modification and Control of Early Development in the 

 Frog 312 



No. 6. DECEMBER, 1919. 

 HAUSMAN, LEON A. The Orange Striped Anemone (Sagartia 



lucitz, Verrill): An Ecological Study . , 363 



FOOT, KATHARINE. Preliminary Note on the Spermato- 



genesis of Pediculus vestimenti 371 



FOOT, KATHARINE. Determination of the Sex of the Offspring 



from a Single Pair of Pediculus vestimenti 385 



HYMAN, L. H. Physiological Studies on Planaria, III 388 



HYMAN, L. H. On the Action of Certain Substances on 



Oxygen Consumption 44 



