LOW TEMPERATURE DEVELOPMENT OF FUNDULUS 4()3 



but abiiorinalities are very frequent and show the remarkable 

 range of characters described above. 



It seems, then, that the causes of the observed abnonnaUties 

 in development may be referred to these conditions: (a) abnor- 

 mahties in imclear composition and in the distribution of dif- 

 ferentiated nuclear substances ; (b) abnormal distributions and as- 

 sociations of two more evidently differentiated cytoplasmic sub- 

 stances; (c) abnormal associations between nuclear and cyto- 

 plasmic substances, either or both of which may be abnormal 

 in its own composition as compared with the corresponding 

 materials in the regularly developing egg. 



In a word this means that the organization of any part of the 

 early organism may be disturbed, and that such disturbances 

 are the causes of abnormal and monstrous development. That 

 development can occur at all under such circumstances indicates 

 remarkable regulatory properties of the egg substance. The 

 complete lack of specificity in the effects of the cold indicates 

 that the disturbance is profound and that it affects the funda- 

 mental organization of the ovum rather than any especially dif- 

 ferentiated representative substances or anlagen, which, more- 

 over, have been shown by other evidence not to exist in the 

 Teleost ovum (Morgan, '93, Sumner, '04). 



Going a step back of these observations to the query as to 

 just how the low temperature can produce such disturbances, we 

 can at this time make suggestions only in very general terms. 

 It is evident that not all of the processes of development or 

 parts of the developmental mechanism are affected similarly, 

 for that would lead to development normal in all save its rate. 

 Some physical or chemical processes or structures must be more 

 extensively interrupted or altered than others, as a result of the 

 lowered temperature. They are thrown out of their normal re- 

 lations to the other processes or parts of the mechanism and 

 sooner or later a whole train of consequences may become evi- 

 dent. It is very important to note, however, that the substances 

 or processes thus affected are not to be thought of as specific 

 tissue — or ' organ-forming substances' nor as differentiated, cellu- 

 lar or formed rudiments or anlagen, but as elements or factors 



