THE ARGUMENTS FROM EMBRYOLOGY. 451 



allow for. Then, further, there comes the lateral deviation 

 due to wind, which may be appreciable if the wind is strong 

 and the range great. To introduce him all at once to the 

 correct conception thus finally reached would be impossible: 

 it has to be reached through successive qualifications. And 

 that which holds even in this simple case necessarily holds 

 more conspicuously in complex cases. 



The title of the chapter suggests a metdphor, which is, 

 indeed, something more than a metaphor. There is an em- 

 bryology of conceptions. That this statement is not wholly 

 a figure of speech, we shall see on considering that cerebral 

 organization is a part of organization at large; and that the 

 evolving nervous plexus which is the correlative of an evolv- 

 ing conception, must conform to the general law of change 

 conformed to in the evolution of the whole nervous structure 

 as well as in the evolution of the whole bodily structure. As 

 the body has at first a rude form, very remotely suggesting 

 that which is presently developed by the superposing of modi- 

 fications on modifications ; so the brain as a whole and its con- 

 tained ideas together make up an inner world answering with 

 extreme indefiniteness to that outer world to which it is 

 brought by successive approximations into tolerable corre- 

 spondence ; and so any nervous plexus and its associated hypo- 

 thesis, which refer to some external group of phenomena under 

 investigation, have to reach their final developments by 

 successive corrections. 



This being the course of discovery must also be the course 

 of exposition. In pursuance of this course we may there- 

 fore fitly contemplate that early formula of embryological 

 development which we owe to von Baer. 



128. Already in 52, where the generalization of von 

 Baer respecting the relations of embryos was set forth, there 

 was given the warning, above repeated with greater distinct- 

 ness, that it is only an adumbration. 



In the words of his translator, he "found that in its earliest 



