EARLY DEVELOPMENT IN THE FROG. 353 



logical axes. Anterior, medial, dorsal regions, because of their 

 higher metabolic rate are more susceptible to the inhibiting 

 conditions and hence are more affected. 



Bataillon (1901) studied the abnormal development of the 

 frog in isotonic solutions of cane sugar, NaCl, and a number of 

 other salts and reached the conclusion that osmotic pressure and 

 the consequent withdrawal of water from the developing embryo, 

 is the effective cause of abnormalities. Jenkinson (1906) showed 

 that solutions of a large number of substances, isotonic with 

 0.625 per cent. NaCl, do not produce the same, but markedly 

 different effects. It may be pointed out however that these 

 effects differ not in kind, but in degree, and are on the whole 

 readily interpreted in terms of differential susceptibility. And 

 it may be remarked here that the large number of abnormalities 

 in the frog described during the past quarter of a century which 

 have been produced by experimental means may all be rationally 

 interpreted in these terms and readily brought into relation with 

 the axial gradients. Jenkinson's conclusion was that the ab- 

 normalities produced covering most of the modifications known 

 in amphibian teratology were not to be attributed to the os- 

 motic pressure of the solutions but were due to their chemical 

 or physical properties. Morgan who has done much work on 

 abnormal development in the frog, stated, (1906) in speaking of 

 the osmotic and chemical effect of salt solutions on the frog egg, 

 that: "It is probable that the effect is a double one; in part 

 chemical, in part osmotic." 



There can be little doubt that certain substances especially 

 in high concentrations, do have a physical as well as a chemical 

 effect upon protoplasm. Furthermore, in a highly specialized 

 egg like that of the frog where a considerable volume of relatively- 

 inert matter (yolk) is localized in one hemisphere, high osmotic 

 pressures such as exist in solutions of certain electrolytes and 

 other substances in concentrations high enough to cause markedly 

 abnormal development, and substances that have a solvent action 

 on the yolk (alcohol, e.g.), may in -extreme cases set up secondary 

 disturbances of a mechanical sort such as partly or wholly to 

 obscure the general susceptibility relations. But, it is especially 

 to be noted that those agents which, in extreme concentrations 



