LOW TEMPERATURE — DEVELOPMENT OF FUNDULUS 467 



sentative, definitive, orf2;aiiizecl rudiment of the anterior tip of 

 the central nervous system, and further that it possesses a sensi- 

 tivity to general nutritional disturbances which is also specific, 

 i.e., not shared equally by other rudiments which must also be 

 assumed to be present at this time. But it is well known that 

 the Teleost ovum is of the indeterminate type, and injury or 

 removal of whole blastomeres of the normal cleavage group 

 causes no later defects or abnormalities in the developing em- 

 bryo. The assumption of specificity in the action of nutritional 

 effects in connection with cyclopia, is further negatived by the 

 great variety of the results following chemical treatment. I 

 have already pointed out the great variety of abnormalities and 

 monstrosities observed by Stockard, Werber, and others, appear- 

 ing under the same experimental conditions. The only sugges- 

 tion of actual specificity is that of Stockard ('10, p. 369) that 

 treatment with certain percentages of alcohol gives, among the 

 surviving embryos 90-98 per cent with abnormal eyes, generally 

 Cyclopean. But he does not say that other defects may not also 

 be found in these or other embryos similarly treated, indeed on 

 the contrary he mentions a great variety of ear, brain and other 

 defects which may either accompany eye-defects or appear in- 

 dependently of them, under similar treatment. Moreover, the 

 expression 'eye defects' covers a number of different conditions, 

 not all of which can be referred to the cause which he assumes 

 for cyclopia, namely, the inhibition of the development of the 

 median anterior tip of the central nervous system. To find a 

 great variety of abnormalities among embryos subjected to the 

 same treatment leads definitely to giving up the idea of specific 

 reactions of the rudiments of such structures to the unusual con- 

 ditions. To relate the appearance of such a variety of abnor- 

 malities during later development of the embryo, to the effects 

 of the treatment upon some specific parts of the materials of the 

 cleavage group is, therefore, to assume the existence of differ- 

 entiations during cleavage which have been shown not to exist, 

 and then to requu'e further that each or any ^ or all of these may 

 be specifically affected, which is to say that there is no speci- 

 ficity at all in the action or in the reaction. 



