iv COXTEXTS OF VOLUME LIII 



No. 4. OCTOBER, 1927. 



HORNING, BENJAMIN, AND TORREY, HARRY BEAL. Thyroid 



and Gonad as Factors in the Production of Plumage 



Mclanins in the Domestic Fowl 221 



CHAMBERS, ROBERT, AND POLLACK, HERBERT. The pH of 



the Blastoccclc of Echinodcrm Embryos 233 



BASKERVILLE, M. L. The Permeability of Frog Skin to 



Urea: 



I. The Influence of NaCl and CaCh 239 



//. The Effect of Dextrose and Sucrose 247 



DIECKMANN, JOHANNA M. The Cloaca and Sperrnathcca of 



Gyrinophilus porphyriticus 258 



DIECKMANN, JOHANNA M. The Cloaca and Spermatheca of 



Hemidactylium scutatum 281 



WHEDON, ARTHUR D. Tlie Structure and Transformation 



of the Labium of Ana.v junius 286 



No. 5. NOVEMBER, 1927. 



ALLEE, W. C, AND SCHUETT, J. F. Studies in Animal Ag- 

 gregations: The Relation between Mass of Animals and 

 Resistance to Colloidal Silver 301 



CKABB, EDWARD D., AND RUBY, M. Polyvitclliny in Pond 



Snails .- 318 



ANDERSON, LOUISE A. The Effect of Alkalies on tlic Oxy- 

 gen Consumption and Susceptibility of Planaria doroto- 

 ccphala 327 \ 



FRIEDMANN, HERBERT. A Case of Apparently Adaptive Ac- 

 celeration of Embryonic Growth-Rate in Birds 343 



CORRINGTON, JULIAN D. Commensal Association of a Spider 



Crab and a Medusa 346 



GATES, G. E. Regeneration in a Tropical Earthworm Per- 



iony.r c.vcai'atus E. Perr 351 



BKINLEY, FLOYD JOHN. Studies on tlie Physiological Ef- 

 fects of Hydrogen Cyanide 365 



HILDEBRAND, SAMUEL F. Sc.r Ratio in Gainbusia 390 



