48 HAROLD SAXTON BURR 



a correlation between structure and function (page 34). The 

 physiological experiments showed that larvae over four weeks 

 old could detect food by the sense of smell. Correlated, then, 

 with the beginning of functional activity of the nasal epithelium, 

 there exists in operated forms the beginning of a difference in 

 the growth rates of the two hemispheres. 



The above facts suggest that there is inherent in the tissue 

 of the central nervous system a certain potential for develop- 

 ment and differentiation. This potential carries the growth up 

 to a certain point at which all the parts of the brain are present. 

 The further growth then l)ecomes dependent on the functional 

 activity of the parts. 



The conclusion stated above can not be considered final. A 

 more extensive study with special methods, of the fiber tracts 

 involved must be engaged in before any final judgment can be 

 reached. At present such a study is under way. It is planned 

 to carry the operated larvae through metamorphosis as it is 

 evident the effects become more pronounced with age. 



The writer takes this opportunity to express his appreciation 

 of the criticism and suggestions made by Dr. Harrison during 

 this investigation. 



SUMMARY 



The physiological tests of the reactions to food of normal and 

 noseless larva show: — 



1) That normal larvae will react positively to sand 

 grains that move in the water. 



2) That normal larvae will react positively to food 

 that is not moving. 



3) That noseless larvae will react positively to sand 

 grains but not to motionless food. 



4) That eyeless larvae will react positively to food 

 that they cannot see and will not react to moving sand 

 grains. 



The effect of the absence of the nasal sac on the form of the 

 skull is shown in the complete collapse of the cartilages that 

 normally surround the sac, this collapse being due to the absence 



