No. 3. APRIL 



H. D. Good ALE. Studies on hybrid ducks. Nine figures: two plates 241 



Hans Przibram. Experiments on asymmetrical forms as affording a clue to 



the problem of bilaterality. Eleven figures: one plate 255 



C. M. Child. Studies on the dynamics of morphogenesis and inheritance in 

 experimental reproduction. I. The axial gradient in Planaria doroto- 

 cephala as a limiting factor in regulation. Forty-one figures 265 



Sergius Morgulis. Contributions to the physiology of regeneration. IV. 



Regulation of the water content in regeneration. Seven figures 321 



No. 4. MAY 



G. Harold Drew. Experimental metaplasia. I. The formation of colum- 

 nar ciliated epithelium from fibroblasts in Pecten. Three plates 349 



Helen Dean King. The effects of semi-spaying and of semi-castration on 

 • the sex ratio of the albino rat (Mus norvegicus albinus) 381 



^ Edwin G. Conklin. The organization of the egg and ' ' e development of 



single blastomeres of Phallusia mamillata. Fourt r .res 393 



. Francis B. Sumner. The adjustment of flatfish to various backgrounds. A 



study of adaptive color change. Thirteen plates 409 



E. Newton Harvey. Studies on the permeability of cells. Three figures. . 507 



, Lorande Loss Woodruff. The effect of excretion products of Paramaecium 



on its rate of reproduction. Eleven figures 557 



