LOW TEMPERATURE — DEVELOPMENT OF FUNDULUS 469 



Embryonic differentiations having been begun before that time, 

 the way might be opened to a specificity of action upon some 

 part requiring a large supply of energy and material. The later 

 the abnormal conditions act, the more likely are they to be 

 specific in their action. But in the absence of definite proof of 

 such a cause, it is on the whole much easier to interpret mon- 

 strosities, even among the Mammals, as resulting from organi- 

 zational disturbances produced by the presence or absence of 

 some definite chemical environment, whether that be nutritional 

 or not. And such a chemical stimulus might be operative not 

 onlj^ after, but also before implantation, when the extent of the 

 resulting abnormality might be very great, so great as to result 

 in the formation of a 'complete monster.' I should not, how- 

 ever, oppose the idea that mammalian monsters may be due, 

 in some cases to nutritional defects: in this connection I should 

 merely suggest that the observed facts do not exclude the pos- 

 sibility of a general organizational disturbance as the cause of 

 monstrous development in this group, and that even in the pla- 

 cental mammaUan embryo, although with less hkelihood than in 

 oviparous forms, the nutritional disturbance, when it is known 

 to exist, may itself be a result rather than a cause of the de- 

 ranged organization. 



But it seems, in the hght of subsequent observations, that it 

 was a mistake to extend this interpretation of the causes of 

 abnormal development so generally to other classes of verte- 

 brates and to say that such abnormaUties result from conditions 

 "which affect the nutrition and impair the growth of the em- 

 bryo" (Mall '08, p. 52) or which "tend to lower the develop- 

 mental vigor of the embryo" (Stockard, '13 a, p. 83), or that 

 "a certain amount of energy is necessary for differentiation of 

 the eye to take place .... but when the required energy 

 for any reason is not available the eyes are incapable of any dif- 

 ferentiation" (Stockard, '13 b, p. 271). Such a statement seems 

 to leave unexplained such cases as have been observed both by 

 Werber and myself, where portions of eyes, fragments of optic 

 cups, lenses, or even fairly complete eyes, may be found either 

 ^vithout other true tissues or organs being differentiated, or 

 with scattered parts of other organs and bits of tissue. 



