OF THE NERVOUS SYSTEM. 83 



duced by the curvature downwards of the early Mammalian 

 head.* 



If I have determined aright the morphological relations of 

 these two forms of nervous system, we shall have advanced a 

 step in our conceptions of the anatomico-physiological re- 

 lations of the annulose and vertebrate animals, and this 

 without losing sight of the fundamental differences, develop- 

 mental and structural, between them. The researches of 

 Milne-Edwards, and of Newport and others, on the annulose 

 nervous axis may thus be physiologically associated with 

 those of Wagner, Schroeder Van der Kolk, Owsjannikow, 

 Jacobowitsch, and Kupffer, on the cerebro-spinal axis ; and 

 we may now legitimately employ the annulose animal in the 

 morphological investigation of the vertebrate skeleton. 



Omitting, for the present, the consideration of the mode 

 in which the nervous systems in the Tunicata, Eotifera, and 

 Entozoa, are reducible to the typical annulose form, I pro- 

 ceed to make some general morphological statements, based 

 to a certain extent on the principle indicated in this, and 

 introductory to the two following communications : 



1. The morphology of any one organic system in the 

 annulose or vertebrate animal, cannot be safely or satis- 

 factorily investigated, without constant reference to the 

 others. That it must be so is evident from the fact, that all 

 the organic systems are dependent on one another, in the 

 constitution of the organism. 



2. All sound morphological inquiry demands constant 

 reference to the series of embryo, as well as of adult forms. 



3. As morphology deals with forms and relations of posi- 

 tion, it demands a careful selection of terms, and a methodised 



* I have introduced the hypothesis of a vertebrate neural mouth (cast aside 

 in the course of my examination of the subject), because I believe it will be 

 found to involve relations of importance in the anatomico-physiological in- 

 vestigation of the pre-stomal and post-stomal portions of the vertebrate and 

 annulose cephalic nervous masses. 



