IV CONTENTS. 



No. 4. OCTOBER, 1921 



HERTIG, MARSHALL. Attempts to Cultivate the Bacteroids 



of the Blattidce 181 



\YELCH, PAUL S. Bifurcation in the Embryos of Tubifcx. . 188 



LUND, E. J. Oxygen Concentration as a Limiting Factor in 



the Respiratory Metabolism of Planaria agilis 203 



DEDERER, PAULINE H. The Behavior of Cells in Tissue Cul- 

 tures of Fundulus heteroditus with Special Reference to 

 the Ectoderm 221 



LEWIS, MARGARET R. The Presence of Glycogen in the Cells 

 of Embryos of Fundulus heteroditus Studied in Tissue 

 Cultures 241 



No. 5. NOVEMBER, 1921 



VAN DER HYDE, H. C. On the Influence of Temperature on 

 the Excretion of the Hibernating Frog, Rana virescens 

 Kalm 249 



GLASER, OTTO. Note on the Pigment of Arbacia Egg-secre- 

 tion 256 



JEWELL, F. M. Sex Ratios in Fcctal Cattle 259 



KLUGH, A. BROOKER. A Correction Concerning the Life 



Zones of Canada 272 



WOODWARD, ALVALYN E. The Parthenogenetic Effect of 

 Echinoderm Egg-secretions on the Eggs of Nereis lim- 

 bata 276 



HARVEY, E. NEWTON. Studies on Biolumincscence, XIII . . . 280 



FASTEN, NATHAN. The Explosion of the Spermatozoa of the 



Crab Lophopanopcus bell us (Stimpson) Rathbun 288 



EIGENMANN, C. H., AND ALLEN, W. R. A Leaf Mimicking 



Fish 301 



No. 6. DECEMBER, 1921 



UHLENHUTH, E. The Effect of Iodine and lodothyrine on 

 tJie Larva of Salamanders. II. The Relation bet-ween 

 Metamorphosis and Limb Development in Salamander 

 Larvce 307 



CHAMBERS, ROBERT. Microdissection Studies, III. Some 

 Problems in the Maturation and Fertilization of tJic 

 Echinoderm Egg 318 



BELLAMY, A. W. Note Concerning the Origin of Polarity 



in the Frog's Egg. A Correction 351 



