Contents of Volume XLIV 



No. i. January, 1923 



Just, E. E. The Fertilization-Reaction in Echinarachnius 



parma, VI. The Necessity of the Egg Cortex for Fertiliza- 1 

 Hon 



Just, E. E. The Fertilization-Reaction in Echinarachnius 



parma, VII. The Inhibitory Action of Blood 10 



Just, E. E. The Fertilization-Reaction in Echinarachnius 



parma, VIII. Fertilization in Dilute Sea-Water 17 



Kepner, Wm. A. and Reynolds, B. D. Reactions of Cell- 

 Bodies and Pseudopodial of Fragments of Difflugia 22 



No. 2. February, 1923 



Lillie, Frank R. Supplementary Notes on Twins in Cattle. 47 

 Glaser, Otto. Copper, Enzymes, and Fertilization 79 



No. 3. March, 1923 



Zeleny, Charles. The Temperature Coefficient of a Hetero- 

 zygote with an Expression for the Value of a Germinal 

 Difference in Terms of an Environmental One 105 



Sivickis, P. B. Studies on the Physiology of Reconstitution 



in Planaria lata, with a Description of the Species 113 



No. 4. April, 1923 



McNair, George T. Motor Reactions of the Fresh-Water 



Sponge, Ephydatia fluviatilis 153 



Allee, W. C. Studies in Marine Ecology. I, The Distribu- 

 tion of Common Littoral Invertebrates of the Woods Hole 

 Region . 167 



Lambert, W. V., Rice, W. S., and Walker, H. C. A. 

 Food and Partheno genetic Reproduction as Related to the 



Constitutional Vigor of Hydatina senta 192 



iii 



