2IO STRONG. [Vol. X. 



Finally, without a recognition of these nerve components, 

 embryological research, it appears to me, becomes partly 

 meaningless. The fact that certain ganglia are connected, in 

 course of development, with epiblastic thickenings while others, 

 apparently, are not, is correlated with some difference, structural 

 and physiological, which either exists now or has existed. How 

 can we determine what value to attach to such differences of 

 origin until we know with what differences in the adult 

 structure they are correlated and, as a consequence, what was 

 the original cause of their appearance } A knowledge of the 

 structure itself may be fairly considered a necessary preliminary 

 to ascertaining its embryological origin. 



Department of Biology, 



Columbia College, July, 1894. 



