LOW TEMPERATURE — DEVELOPMENT OF FUNDULUS 471 



proliferation of ectoderm cells, the foriiuitioii of larp;e masses of 

 erythrocytes, et cetera. Apparently the only way to interpret 

 such conditions as due to some defect is to have recourse to 

 the interpretative method employed by some geneticists (with 

 the difference, however, that there it may be clearly justified) 

 and say that when abnormal development occurs it is due to a 

 defect in that which would have kept it normal. But that 

 would merely be to say that abnormal development occurs. 

 And it should be recalled just here that Loeb ('15) noticed 

 that eyeless embryos developing from a cross between Fundulus 

 and Menidia reached that condition after passing through 

 earlier stages in which the eyes appeared to be normal. In such 

 instances anophthalmia is certainly not due to any original 

 destruction of ' ophthalmoblastic anlagen.' 



Loeb occasionally inclines toward this nutrition hypothesis 

 in explanation of some abnormalities and points out that, since 

 iji most of his observed instances of anophthalmia circulation 

 also is lacking, "the inference is possible that the anomalous 

 condition of the eye may be due to lack of circulation" ('15, p. 

 67). But the large number of instances in which the eyes may 

 develop normally in the complete absence of circulation renders 

 such an inference untenable. 



A rather significant test of the nutrition hypothesis, or at 

 least of certain phases of it, can be found in those cases where 

 the embryo develops without a heart or without a circulation. 

 Here is certainly a profound disturbance of the nutritive rela- 

 tions of the entire embryo. \ATiatever the primary cause of 

 such a lack, the conditions should, on this hypothesis,, be accom- 

 panied or followed by marked and varied abnormalities. If 

 nutritional disturbances so easily affect development as the gen- 

 eral hypothesis requires, such embryos should certainly produce 

 'complete monsters' capable of but a brief existence. It is often 

 the case that embryos lacking these organs are also defective 

 in various other ways, but it not infrequently happens that such 

 embryos may develop with a high degree of normality in all other 

 respects and when removed from the egg membranes may con- 

 tinue to hve and react almost normally for some time. 



