314 A. W. BELLAMY. 



the action of the solutions." Werber (1915, 1916, 1917) ob- 

 tained all the known types of terata in Fundulus by using 

 substances usually found among the products of destructive 

 metabolism, viz., butyric acid, acetone, urea, lactic acid, etc. 

 In the concentrations used he found butyric acid and acetone, 

 especially the latter, somewhat more effective than the other 

 substances in the production of monstrous development. Werber 

 looks upon abnormal development as due to a " blastolytic " 

 action of the deleterious agent upon the primordial regions of 

 the eggs, especially those at the anterior end of the body. 

 Kellicott (1916) has secured the usual wide variety of terata in 

 Fundulus simply by subjecting the early egg stages to the action 

 of low temperature. He is inclined to look upon teratogenesis 

 as being due in some way to a "disorganization" of the egg 

 materials. Newman (1917) noticed the same range of ab- 

 normalities among his heterogeneous Fundulus hybrids and 

 applied Child's axial gradient theory to the interpretation of 

 these and other terata seen in teleosts produced by chemical 

 and physical agents. 



Perhaps enough has been said by way of a preliminary state-, 

 ment to indicate the essential similarity of experimentally pro- 

 duced monsters regardless of the methods employed in obtaining 

 them. Likewise a little reflection on the various theories ad- 

 vanced to account for monstrous development makes apparent 

 the lack, hitherto, of an adequate basis for a rational interpreta- 

 tion of them. 



It is the purpose of this report to attempt an analysis of the 

 problem of physiological axiation and teratogeny in the frog 

 from a physiological point of view. It considers the general 

 problem of physiological axiation, the origin of polarity, and 

 presents data on the modification and control of early develop- 

 ment in the frog on the basis of differential susceptibility. 



II. MATERIAL AND METHODS. 



i. The Susceptibility Method. Observations on many species 

 of animals and plants have shown that definite and characteristic 

 differences in susceptibility to a wide variety of physical and 

 chemical agents, within certain limits of concentrations or in- 



