LOW TEMPERATURE — DEVELOPMENT OF FUNDULUS 461 



the general chemical reactions underlying development but not 

 directly related to the income of the embryo, such as nuclear 

 differentiation, mitosis, distribution of nuclear and cytoplasmic 

 substances, specification of protoplasmic areas, et cetera, are 

 evidently not included under the terms nutrition and growth as 

 used here. 



Essentially the same idea is contained in Stockard's hy- 

 pothesis of the causes of the defects observed in Fundulus after 

 chemical treatment, namely, that such treatment tends to lower 

 the developmental vigor of the embryo, this lack of vigor being 

 subsequently shown by the failure of certain structures to de- 

 velop normally. This hypothesis is formulated chiefly in con- 

 nection with the explanation of optic defects, particularly cy- 

 clopia. "A certain amount of energy is necessary for differen- 

 tiation of the eye to take place .... but, when the re- 

 quired energy for any reason is not available the eyes are inca- 

 pable of any differentiation" ('13 b, p. 271). In the absence of 

 any other evidence for such a deficiency in available energy on 

 the part of the embryo, such an explanation comes to little 

 more than a statement that the eyes do not develop. I can not 

 be certain whether or not it is intended that this explanation 

 should be applied to the other abnormalities observed by him, 

 regarding which, however, no other suggestion is made. But 

 as I shall show there are some difficulties in making a general 

 application of this idea in explaining all of the defects noted in 

 his experiments with various chemical substances. 



Using a butyric acid or acetone treatment, Werber ('15 a, 

 '16) secured not only abnormaUties similar to those recorded by 

 Stockard, but also a wide range of the same general types, and 

 in many instances the same specific types, as those which I have 

 found to follow the action of a low temperature. Werber be- 

 lieves that there are some factors common to the morphogenesis 

 of all the diverse abnormahties and monstrosities observed in a 

 given experiment. He applies the term ' blastolysis' collectively 

 to the factors involved and believes that there occurs, as a con- 

 sequence, a destruction or dispersal of parts or all of the germ's 

 substance. 



